VTInotat
Number: J 11 Date: 91-12-02
Title: Protection of road-railway grade crossings by means of
mobile barriers - some preliminary ideas
Authors: Erik Lindberg
Bertil Morén Thomas Turbell
Division: Railway Division
Project No: 20319 - 0
Project name: Mobile Barrier Concepts to Shield Railway Crossings
F'manced by: Swedish National Rail Administration (Banverket)
Distribution: free
Statens Väg- och trafikinstitut
ä Våg' 06/7 af/k' Pa: 581 01 Linköping. Tel. 013204000. Telex 50125 VTISGIS. Telefax 013-14 1436
PREFACE
This is the final report from a project initiated and ñnanced by the Swedish National Rail Administration (Banverket).
The leader of the project has been Erik Lindberg at the Swedish Road and Traffic Research Institute (VTI). Bertil Morén and Thomas Turbell (also at VTI) have assisted in the planning and administration of the project, and they have also oo-authored this report. Tarja Magnusson (VTI) has carried out a search for literature on mobile barrier concepts.
Special thanks are due to Per Sillén at the Planning Department of the Swedish National Rail Administration for coming up with many good ideas concerning possible barrier types to be considered in the project, and to Hayes E. Ross Jr. and Dean L. Sicking at Scientific Inquiry Inc. , Texas, USA for carrying out the technical feasibility study which is included in the Appendix to this report.
CONTENTS
SUMMARY I
SAMMANFATTNING (SWEDISH SUMMARY) H
1 BACKGROUND AND SCOPE OF THE PROJECT 1
2 FEASIBILITY OF MOBILE BARRIER CONCEPTS 4
3 SUPPLEMENT TO THE TECHNICAL FEASIBILITY STUDY 6
4 ADDITIONAL COMMENTS ON PROPOSED BARRIER TYPES 8
4. 1 Vulnerability 8
4.2 Acceptability 9
5 CONCLUSION 12
Appendix: Mcbile barrier concepts to shield railroad crossings" by Hayes E. Ross Jr and Dean L. Sicking, Scientific Inquiry Inc., Texas, USA
PROTECTION OF ROAD-RAILWAY GRADE CROSSINGS BY NIEANS OF MOBILE BARRIERS
Some preliminary ideas
by Erik Lindberg, Bertil Morén och Thomas Turbell Swedish Road and Traffic Research Institute (VTI) 8-581 01 LINKÖPING Sweden
SUlVIlVIARY
The study discusses some preliminary ideas concerning the possibility to use some type of mobile barriers to prevent collisions between trains and road vehicles at grade crossings. The discussion has presupposed that such barriers are only meant to be used in cases where safety requirements are especially high and a grade separated crossing cannot be built.
Two literature searches were carried out butrevealed no trace of any current use of mobile barriers that would withst the impact of road vehicles at road-railroad grade crossings.
A technical feasibility study was made of five different mobile barrier designs, and a sixth design was also discussed briefly. Of the designs discussed, three had a rigid construction whereas the remainder had energy-absorbing properties. All of the designs were judged to be technically and economically feasible for shielding grade crossings. However, objections could be raised against all of the designs and it was proposed that a more thorough risk analysis should be carried out before any further development of a mobile barrier concept takes place. Considerations concering among other things the possible risks which a mobile barrier might impose on motorists and others suggested that an energy-absorbing arrestor net might be the design which is most worthy of further study among the barrier concepts discussed in this project.
SKYDDANDE AV PLANKORSNINGAR MED HJÄLP AV RÖRLIGA GENOMKÖRNINGSSÃKRA HINDER
En preliminär idéstudie
av Erik Lindberg, Bertil Morén och Thomas Turbell Statens väg- och trañkinstitut
LINKÖPING
SAWANFATTNING
Denna studie presenterar några preliminära synpunkter på ett antal idéer som framförts beträffande möjligheten att använda olika typer av rörliga hinder i syfte att förhindra kollisioner mellan tåg och vägfordon i plankorsningar. De olika lösningar som diskuteras har förutsatts vara avsedda endast för sådana fall där säkerhetskraven är speciellt höga och där en planskild korsning inte är möjlig att åstadkomma.
Två olika litteratursökningar har genomförts utan att resultera i några uppgifter om faktiskt förekommande användning av rörliga genomkörningssäkra hinder i samband med plankorsningar.
I projektet har fem olika utföranden av sådana hinder studerats med avseende på teknisk genomförbarhet, och en sjätte möjlighet har också kortfattat diskuterats. Tre av de hindervarianter som belysts har en stel konstruktion medan återstoden har energiupptagande egenskaper. Samtliga utföranden bedömdes vara tekniskt och ekonomiskt realiserbara. Samtidigt konstaterades dock att inget av de utföranden som diskuterats var invändningsfritt och att en mera fullständig riskanalys behöver göras innan något eventuellt utvecklingsarbete påbörjas. Preliminära överväganden avseende bland annat möjliga risker som olika typer av rörliga hinder kan tänkas utsätta vågfordonsförare och andra för gav vid handen att ett energiupptagande nät syns vara den lösning som i första hand kan vara värd att studera vidare.
1 BACKGROUND AND SCOPE OF THE PROJECT
Collisions between road vehicles and trains at highway-railroad grade crossings constitute one of the more serious safety problems of railway traffic. In Sweden the number of such collisions is about 80 per year. Sweden has more than 15 000 grade crossings and the Swedish National Rail Administration has an ongoing program for reducing this number and for increasing safety at grade crossings in general.
With an increase in the number of high-speed trains, the crossing safety problem becomes even more prominent. Although higher train speeds may not have any dramatic effects on the frequency of collisions with road vehicles, the severity of the consequences of derailments caused by such collisions can be expected to increase.
Since not even sophisticated devices for warning motorists are sufñcient to prevent all collisions at grade crossings, the preferred ways of increasing safety are to close down minor crossings and to build more grade separated crossings. Building a grade separated crossing is however very expensive (the cost is usually between 5 and 15 million SEK). Apart from the high cost, some grade crossings may be virtually impossible to replace with grade separated crossings due to geotechnical conditions, slopes, or insufñcient space (mainly in densely built areas).
In cases where a grade separated crossing cannot be built, it might however still in principle be possible to avoid collisions by physically preventing road vehicles from entering grade crossings immediately before and during the passage of a train. The present project discusses some preliminary ideas concering possible types of mobile barriers which might conceivably be used for this purpose. The scope of the project is strictly limited to a discussion of the (mainly technical) feasibility of some such concepts. This means that issues concerning general crossing safety and the question whether it would be appropriate from a societal point of view to install such mobile barriers are left out of the discussion. Furthermore, the discussion does not pertain to grade crossings in general but only to cases where: a) There is a requirement for
maximum safety due to high-speed train traffic and b) A grade separated crossing cannot be built for' one or more of the reasons mentioned in the preceding paragraph.
It should also be noted that the discussion of mobile barrier concepts in this report presupposes that such barriers are not the only safety installation at any grade crossing. In addition traditional full-barriers (which do not withstand the impact of a road vehicle) and devices that will detect the presence of a road vehicle in the crossing area are supposed to be used. The role of the mobile barriers should be viewed as being an element in the following sequence of events: 1) Traditional full-barriers are activated by an approaching train, 2) After the traditional barriers are fully closed, a test for the presence of road vehicles in the crossing area is carried out whilst the train is still at a sufñcient distance from the crossing in order to be possible to stop in time, 3) Given that there are no vehicles in the crossing area, the mobile barrier (which is supposed to be located between the full-barriers and the tracks) is activated, and 4) The train arrives at the crossing.
The preliminary nature and- limited budget of the present project have made it necessary to select only a few possible types of mobile barrier concepts for consideration. Performing crash tests and the like has been far beyond the scope of the project, which means that the types of barriers which have been considered are in most cases devices for which such data are already available. It should also be stressed that the scope of the project has been limited to a very preliminary evaluation of the different types of barriers described in this report. The bulk of the project budget has been spent on a technical feasibility study carried out by Dr Hayes E. Ross Jr. and associates at Scientific Inquiry Inc. , Texas.' This study has consisted of a literature review (based on a search in the TRIS computerized information data base) followal by a conceptualization of potential mobile barrier designs. A preliminary analysis was also conducted to estimate performance capabilities and costs of some of the more promising concepts. The main results from the study will be summarized in the next section, and the full report on the study is included in the Appendix.
Besides the literature search conducted as a part of the technical feasibility study, another search was carried out at the Swedish Road and Trafñc Research Institute using the IRRD and NTIS computerized data bases. This search did however not yield any significant additions to the barrier concepts presented in the feasibility study.
2 FEASIBILITY OF MOBILE BARRIER CONCEPTS
The literature searches conducted in this project did not show any record of the use of mobile barriers which would withstand the impact of road vehicles in connection with railroad grade crossings. Such barriers are however in use at e.g. ferry landings and embassies, and they are also used for protecting private
property.
The technical feasibility study has considered two main types of mobile barriers which could be used in order to protect grade crossings (see Appendix for more details about the different types of barriers):
1) Rigid, non-forgiving devices designed to physically prevent the
encroachment of a motor vehicle onto the tracks without regard for the safety of the vehicle' s occupants.
2) Barriers with energy-absorbing properties designed to minimize the likelihood of serious injury to the occupants of an impacting vehicle. The thrust of the feasibility study has been on the latter type of design, and two designs have beenfound worthy of further study. One of these designs is an
"arrestor net" system (sée Figures 4 to 6 in the Appendix) and the other is a
kind of mobile "inertia barrier" (see Figures 7 and 8 in the Appendix). For these two systems calculations of space requirements, capacity to stop vehicles with different masses and impact speeds, forces acting on vehicle occupants, and price ranges have been carried out.
In addition to the two energy-absorbing devices three types of commercially availabe rigid devices have been considered. These are a high security barricade system, a high security bollard system, and a crash rated cable beam barrier (see Figures l, 2 and 3, respectively, in the Appendix). Technical details about these systems have been provided by the manufacturer and are included in the Appendix.
All of the described designs were judged as technically feasible and worthy of further study for possible use at road-railroad grade crossings. The estimated costs of installing the proposed designs range from about one to about three quarters of a million SEK, which means that they compare very favourably to the costs for building a grade separated crossing. It must be noted, however, that maintenance costs are not included in the estimated prices of the mobile barrier designs. Of the two energy-absorbing designs, the arrestor net system was judged to be the most feasible. This is also the design with the lowest estimated costs.
The selection of the different designs considered in the technical feasibility study has been based on the requirement that the barrier should be able to stop vehicles with a weight less than or equal to about 2 000 kg travelling at a speed not exceeding 70 km/h. These requirements were primarily motivated by the fact that most locations where grade separated crossings cannot be built are in densely populated areas with a speed limit of 50 km/h in most cases. However, there may still be a risk that a mobile barrier could be impacted by a considerany heavier vehicle travelling at high speed. The only barrier types which seems to have any chance at all of stopping such a vehicle would be the high security barricade system and the design discussed in the next section of this report. However, even if a few of the discussed designs may have the capacity of stopping quite heavy trucks, some consideration should also be given to what might happen with the load of the truck in such cases. It is for instance possible that the truck load might in some cases disengage and interfere with the train, either by blocking the tracks' or by impacting the body of the train. It should be recalled that the requirement for load retention in this connection is merely 1 G, which would be only maybe 5 % of the deceleration force obtained in the truck body by any kind of rigid barrier.
3 SUPPLEMENT TO THE TECHNICAL FEASIBILITY STUDY At some grade crossings where a mobile barrier might be warranted there may exist one or more unused tracks in addition to the track with high-speed train traffic. Such circumstances may suggest a solution which has not been considered in the technical feasibility study, namely to use some (outdated) rolling railway material (e.g. an old freight car) to shield the crossing.
Such a design has certain merits:
* The "barrier" itself can probably be obtained at very low cost
* It can be loaded to obtain a low center of gravity to prevent it from derailing and thereby interfering with traffic on the main track if hit by a road vehicle. It can also be supplemented with permanent installations (e.g. concrete blocks or very strong steel poles) between the barrier and the main tracks in order to prevent such interference. (If not secured in this way, the mass of the barrier, i.e. 20 to 30 tons if loaded in the suggested way, will probably be insufñcient to stop a heavy truck of about the same weight by which it might potentially be impacted. In a collision of this type it can be assumed that the impulse of the truck and the barrier will remain unchanged. This implies that the truck and the barrier will continue to move together with about 50% of the initial speed of the truck. The forces transmitted through the flanges of the wheels of the barrier and the friction forces between the wheels and the ground will determine how far this configuration will slide before it stops. It can be assumed however that this distance will be far beyond the available space between parallel
tracks.) V
* The proposed design may be used either as a rigid or as an energy-absorbing barrier.
However, it also has drawbacks which, taken together, make it seem less feasible than the remaining designs considered in this project.
First, some kind of system for pulling/pushing the barrier into and out of the crossing would have to be developed. Since the proposed solution would be
possible only for very few crossings, the development costs for such a system are likely to add substantially to the total cost of each installation.
If the barrier is intended to have energy-absorbing properties it would have to be protected by some sort of energy-absorbing device on the side facing the road traffic. In order to give a good protection for small cars at high speeds this device would have to allow for several meters of deformation. This might be achieved by using existing devices, e.g. so called TMA:s (Tka Mounted Attenuators) designed to protect motorists running into the rear end of heavy trucks. These devices are not heavy and should be possible to install without too many problems. They are however quite expensive. In order to adequately bolster the solution discussed in such a way that the occupants of an impacting vehicle would have a sufñcient chance of surviving maybe 4 to 6 units with a width of 2 m each would be needed at a cost of approximately 50 000 SEK each. These units will be destroyed in a collision with even a small car. It might be possible to use other types of attenuators, e.g. steel cylinders or empty oil drums, but in that case it would probably be necessary to perform a series of quite expensive crash tests. Again the costs for this would have to be shared by very few installations.
In addition to these objections, which stem mainly from the fact that the solution is a new and untested one and therefore may prove to be more expensive than expected, this design may also share possible weaknesses with some of the other proposed designs. In the next section, the different barrier types will be discussed with respect to some issues which have not been touched upon so far in this report nor in the technical feasibility study.
4 ADDITIONAL COMNIENTS ON PROPOSED BARRIER TYPES In this section the different proposed barrier designs will be briefly commented on from two perspectives that are not represented in the technical feasibility study. First, under the sub-heading of vulnerability, a few remarks will be made on factors which may cause disturbances in the operation of the different designs. Second, the different barrier types will be discussed in terms of their expected degree of acceptability to the general public.
4.1 Vulnerability
Since the proposed mobile barriers are considered for possible use in Sweden, it is essential that they can be expected to function properly also under winter conditions which may involve quite low temperatures and substantial amounts of snow and ice. Some of the rigid barriers (the barricade and bollard systems) can be obtained with heating systems, which suggests that they may be appropiate for operation under winter conditions. It is possible however that the heating is designed only to keep the hydraulic mechanism operational and therefore will be insufñcient for melting away snow and ice on the outside. The cable beam barrier and arrestor net designs will probably be little affected by winter conditions, provided that the mechanisms for raising and lowering these devices can be kept free from ice. The designs which can be expected to be most vulnerable to malfunctioning due to winter conditions are the inertia barrier and the solution discussed in the previous section of this report. The reason for this is that both designs involve a horisontal motion of the barrier which may be hindered by large amounts of snow and ice. In addition, the energy-absorbing capacity of these devices may be affected (although not necessarily diminished). Regardless of what design or designs are selected for further consideration, testing under winter conditions would seem to be a strong requirement.
Another potential source of malfunctioning which needs to be considered is sabotage. The designs which should be least vulnerable to this source of disturbances are clearly ,the security barricade and bollard systems since they are lowered into the roadway and thus well protected most of the time. All of the
other proposed designs have more or less unprotected moving parts which could possiny be tampered with by someone wanting to interfere with their proper functioning.
Without further testing of at least some of the designs it is difñcult to estimate the frequency of disturbances due to normal wear and tear. Although the rigid barrier types would seem to have an advantage in this respect due to their robustness and few moving parts, it is difficult to tell the different energy-absorbing barriers apart. The arrestor net undoubtedly appears to be the most fragile design, but it must be kept in mind that the weight of the net is only a very small fraction of that of the inertia barrier or the solution described in the previous section. After being forcefully impacted by a road vehicle, all of the suggested designs (except, possibly, the security barricade) would probably be
damaged to such an extent that they would have to be replaced by a new
installation.
4.2 Acceptability
In order for a mobile barrier concept to gain public acceptance it is probably absolutely necessary that the barrier can be operated in a way that does not under any circumstances expose car drivers, passengers, or others to increased risk. Regardless of the actual amount of risk, many of the proposed designs may (especially to people who are unfamiliar with how they are operated) seem to be quite dangerous merely because their appearance suggests that they may be capable of inflicting serious damage to occupants of impacting vehicles. The arrestor net can be expected to have a large advantage over the remaining designs in this respect (provided that the rigid support structure for the net is shielded appropriater by e.g. a guardrail).
A traditional full-barrier installation may in principle be violated by a road vehicle without any directly fatal consequences provided that the violation takes place a sufñcient amount of time before the train arrives at the crossing. Perhaps the most serious objection against the mobile barrier concept (especially the rigid barrier types) is that motorists who otherwise would have had time to clear
10
the crossing by breaking the traditional barrier on the other side may be killed or injured when colliding with a mobile barrier. One way of coming to grips with this argument would be if the mobile barrier could be activated quite rapidly and the activation could be made to more or less coincide with the arrival of the train at the crossing. In that case, the alternative to colliding with the barrier would no longer be to have a chance of being able to clear the crossing in time but rather to hit (or to be hit by) a high-speed train travelling at perhaps 200 km/h. The time required to activate the mobile barrier is at present known only for the rigid designs proposed in the technical feasibility study and appears in those cases to be sufñciently short to make it possible to operate them in this way (see Appendix). Operating mobile barriers so that their activation coincides with the arrival of the train would however reduce their effectiveness in protecting the crossing, since it would then be possible for a road vehicle to break through the traditional full-barrier and get stuck on the tracks before the mobile barrier has been activated (given that the test for the presence of road vehicles in the crossing area would still have to be performed shortly after the activation of the traditional barriers in order to make it possible to stop the train in time). It therefore appears that energy-absorbing devices which can safer be employed for a longer time (i.e. from the test for presence of road vehicles in the crossing area until the passage of the train) may be more feasible than rigid designs.
The proposed use of devices for detecting the presence of road vehicles in the crossing area before the activation of the mobile barrier would seemto preclude the possibility of a vehicle being trapped on the tracks by such a barrier, at least if the barrier can be activated rapidly and the activation takes place immediately after the test for presence has been carried out. For rather slow devices moving horizontally across the road there may however, at least theoretically, be a possibility that a vehicle (after having driven through the traditional full-barrier) will be able to pass the mobile barrier on one side of the tracks but not on the other. This may also be the case with the arrestor net and cable beam barrier designs, but may in that case be less serious because these devices will occupy much less of the crossing area and will therefore leave more room for the trapped vehicle. The arrestor net will furthermore yield somewhat when driven against, and the reluctance to drive against it may actually be somewhat less
11
than in the case of driving through traditional full-barriers in order to clear the tracks because the net has a less solid appearance. It might also be possible to construct the arrestor net barrier in a way that releases the net if impacted from the wrong side.
The risk of trapping vehicles in the crossing area through the use of mobile barriers of the type discussed here should be possible to eliminate if the available space allows the lanes leading into the crossing to be physically separated from the lanes leading out. In that case the barrier could be used only for the former lanes, thus making it possible to clear the crossing at any time by driving through the traditional barriers at the far side of the crossing. This should in principle be possible to achieve with all the types of barrier designs discussed in this report.
Another risk which might have to be considered pertains mainly to heavy and horizontally moving barriers (i.e. , the inertia barrier and the design discussed in the previous section). This risk arises from the possibility that the movement of the barrier itself may to some extent be dangerous to pedestrians (especially to people who for one reason or another are unable to move rather quickly) who happen to be in the crossing area when the barrier is activated. It may also be quite tempting for children playing in the vicinity of the crossing to attempt to take a ride on this type of barriers. Considerations such as these suggest that in order to be regarded as acceptable the horizontally moving barriers would require some kind of surveillance when being activated, something which might add substantially to the total costs of these designs.
Finally, general acceptance of a mobile barrier concept will presuppose that the barrier can be operated in a failsafe manner. Perhaps the most important aspect of this safety is that the barrier must not remain activated when the traditional full-barriers are raised after the passage of the train. In order to ascertain that this is not the case, it may be necessary to include a test for the successful deactivation of the mobile barrier before the traditional barriers can be raised. Although such a test would be most needed for the rigid designs considered in this project, it should be warranted also for the energy-absorbing designs.
12
5 CONCLUSION
All of the mobile barrier concepts (six in all) considered for shielding road-railroad grade crossings in this project appear to be both technically and economically feasible. The different designs considered may however differ signiñcantly with respect to:
a) The amount of additional development and testing required to obtain a fully operational system.
b) The vulnerability to different kinds of external conditions. c) Their degree of acceptability in the eyes of the general public. d) Possible risks imposed on motorists and pedestrians.
Regardless of the particular mobile barrier concept (or concepts) that may be selected for further consideration, careful full-scale testing will need to be undertaken in order to ensure adequate functioning and reliability. In addition to such testing, provided that a mobile barrier concept can be convincingly demonstrated to function properly under varying environmental conditions, a thorough risk analysis would seem to be required in order to avoid any implementation which might expose some people to increased rather than lowered risk. In other words, it will have to be proven beyond reasonable doubt that safety concepts such as those discussed in the present study actually lower overall risk and not just moves the risk from one group of people to another. When considering risks which might be imposed by the types of mobile barriers discussed here it is not difficult to find a number of possible disadvantages with the proposed designs. However, attention should also be given to the risks asso-ciated with the alternative of leaving the crossing protected only by traditional barriers (given that a grade separated crossing cannot be built). The latter alternative involves risks for motorists which may be of the same order of magnitude or even larger than those imposed by the energy-absorbing mobile barrier designs discussed in this report. In addition, the risk of an impacting road vehicle causing a severe train accident with perhaps dozens of killed and/or injured train passengers_ must betaken into account.
APPENDIX
A Report
to
Swedish Road and Traffic Research Institute
entitied
"Mobiie Barrier Concepts to Shieid Raiiroad Crossings"
VTI Project No. 2031902-6
Prepared by
Hayes E. Ross, Jr., Ph.D., P.E.
Dean L. Sicking, P.E. Scientific Inquiry, Inc. 4103 Carter Creek Parkway
Suite A
Bryan, Texas 77802
USA
INTRODUCTION AND OBJECTIVE
An at-grade highway railroad crossing can be a hazardous condition to
highway motorists, to train occupants, and possibly to nearby' motorists,
pedestrians, and occupants of nearby businesses and residents if a derailment
occurs as Ei result of impact with a highway vehicle. Risks increase with
increasing train speed. Large property losses may also be experienced if a
derailment occurs. For various reasons railroad crossing accidents occur even
when active devices such as flashing lights and gates are used to warn motorist
of an oncoming train. The preferred solution to this problem is to separate
highway and train traffic with an overpass or an underpass. Unfortunately, this
solution is often not cost effective. An alternate solution, which is worthy of consideration, would be to use a mobile barrier, in conjunction with the present warning systems, that would restrain most if not all errant motorist who
disregard the warning systems.
Two basic types of mobile barriers could possible be used for this purpose. If the objective is to physically prevent encroachment of a motor vehicle onto the tracks without regard for the safety of the highway vehicle's occupants, a rigid, non-forgiving device such as a series of rigid bollards that would rise
up out of the roadway, could be used. The second type involves barriers with
energy absorbing capabilities, the purpose of which would be to minimize the likelihood of vehicular encroachment onto the tracks while minimizing the likelihood of serious injury to occupants of the impacting vehicle.
The purpose of the study reported herein was to examine the state of the art relative to the subject barriers, to examine the feasibility of using current
or new barrier designs, and to roughly estimate costs of the barriers. To be
noted is that budget constraints limited the scope of the study to only a very
STUDY APPROACH
A literature review was conducted to identify mobile barrier systems with
a potential for application to the subject problem and to ascertain the extent of use of mobile barriers at railroad crossings or at other sites.
While consideration was given to rigid barrier concepts, the thrust of the
study focused on candidate designs having the capability to sajely stop the
impacting vehicle, using NCHRP Report 230 (l) occupant risk evaluation criteria
as a measure of impact severity. For such designs it was assumed the kinetic
energy of the impacting vehicle would not exceed approximately 390 kJ. For
example, this is approximately the kinetic energy a 2,050 kg vehicle would have
at a speed of.70 km/hr. It does not appear feasible to safely stop heavy
vehicles with energy levels in excess of 390 kJ. A rigid barrier of some type
would probably be necessary if it is required to prohibit heavy vehicles with
relatively high speeds from encroaching onto the track. A rigid barrier would
of course pose a high risk of serious injuries to occupants of any impacting vehicle.
Upon review of the literature, two of the more promising energy-absorbing
barrier designs were selected and subjected to an engineering evaluation. The
following section discusses the results of the study and recommendations for further study.
RESULTS AND RECOMMENDATIONS
Literature Review
No record could be found in the literature on the development or use of barriers of the type studied herein for railroad crossings. There is a mobile barrier installation in Texas, although there is no published information on its
performance. It is a vehicuTar "arrestor net" system (2) that is pTaced across
the roadway entrance to a ferry Tanding to prevent errant motorists from driving into the water when the ferry is not present.
FuTT-scaTe crash tests and evaluation of the vehicuTar arrestor net system
have been made at the Texas Transportation Institute (å). The system
successfuTTy and safeTy contained vehicTes weighing up to approximateTy 2000 kg,
impacting at speeds up to approximateTy 100 km/hr. Further anaTysis of this
system was made in the present study and the resuTts are given in a subsequent section.
Interest and use of mobiTe security barriers have increased considerabTy
in the past few years. In generaT, these barriers are designed specificaTTy to
prevent encroachment of most vehicTes, incTuding heavy trucks, without regard to
the safety of the impacting vehicTe's occupants. They are typicaTTy used at
entrances to embassies, other sensitive areas, and private property. Shown in Figures 1 through 3 are three of the types that have been crash tested and are in use around the woer (i). Specifications for each design are given, incTuding their impact capacity. Note that these are commerciaTTy avaiTabTe, pr0prietary
systems.
Use of Riqid Barriers
In the authors' opinion, barriers of the type shown in Figures 1 through 3 coqu be used at raiTroad crossings with a high degree of effectiveness and
reTiabiTity. They woqu require minimaT space. However, they are designed to
be essentiaTTy rigid and non-forgiving. Cost of these systems woqu depend on
various factors, such as roadway width, design vehicTe, design speed, etc. It
is roughTy estimated that a typical instaTTation (barriers on both sides of
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DATA SHEET lnI.,_..._...._551 MODEL TT207
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This barricade system provides an extremely high degree ot security against forced entry by heavrly
loaded trucks or passenger vehicles. ln a tull scale crash test conducted at Brooks Air Force Base in
San Antonio. Texas a TT2073 stopped a 15,000 pound (6803 KG) truck movrng at 50 mph (80.4_kph).
The truck was completely destroyed while the barricade system was tully operational alter the
collision - having sustained only superlicial damage.
Based on these lest results plus an analysis based on the mathematical model ola truck co/lision the ultimate strength of the TT207S has been determined to be'sufficrent to stop and destroy a truck weighing 30,000 pounds (13.608 KG) traveling 50 mph (80.5 kph).
The TT207$ barricade like the wing of a Boeing 747 is built using a caretully engineer-ed _design_ that produces a structure with near maximum strength at minimum weight.. This coupled With a highly dependable Hydraulic Power Unit produces a system ot unequalled reliability and security.
One, Two, Three or Four Barricades can be operated from a single Hydraulic Power Unit. A wide range
of control and override options, automatic operating sequences, sensors, signals and provrsrons to protect against extreme environmental conditions are available as Standard Options.
DELTA Counter Terrorist Barricades are installed and operating in 130 countries guarding some of the most important facilities in the world.
Delta ollers crash rated and crash tested vehicle arrest systems including hydraulic and manual bollards. cable crash beams. sliding and swing gates as well as heavy industrial cantilever rolling gates. gate operators both mechanical and hydraulic. parking gates, passiva tire shredders. velocity and presence vehicle detectors.
Full Engineering, Service and Installation Worldwide
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DATA SHEET 1551
SPECIFICATIONS
BARRIER SIZE: Height.38.0 in (965mm)
Wldth 84 0 to 144 in. (213310 3658mm)
OPERATING TIME:
Ad)ustable from under 30 seconds to 15 seconds,
Emergency Fast Operationless than 1 5 seconds_
DRIVE CONFIGURATION:
The Barricade is raised. lowered and locked int * position by means of preciSion hydraulic Cylinders. The hydraulic control circuit is designed so that at all times in its cycle the barrier is prepared for an impact. There
IS no window of vulnerability" where the barrier might be torced down
by ordinary means.
HYORAULIO POWER SYSTEM:
The hydraulic power system is a self contained source of hydraulic
power to operate one or more barricades either simultaneously or in sets. The components which constitute the system have been carefully selected for their function. long life. availability and dependability. The system is designed and will provide precisely controlled power to the barricade(s) on a reliable basis day in and day out. year in and year out with a minimum of attention or maintenance. The hydraulic power unit stands alone and can be located within 150 feet (45.7m) of the barricades. For distances over 50 feet (15.2m), the hydraulic line size is :ncreased to maintain the operating speedst.
POWER OFF OPERATION:
The TT2OTS can be furnished with a special hydraulic pressure circuit which has SuffiCient reserve capacity to operate the barricade(s) even during a power failure. The barriers are operated by manually shitting the control valvei's).
MODEL TT207S
OPERATING VOLTAGE/POWER CONSUMPTION:
Hydraulic Power Unit: 3 HP (2.8 KW) (Std unit)
208-230/460 VAC - 3 PH - 60 HZ 220/380/440 VAC - 3 PH - 50 HZ Single phase available on request
50 VA * ti:) VA per barrier
115/230 VAC - l PH - 50/60 H2 50 VA
24 VAC (Std). 24 VDC (Optional)
NOTE: Both the hydraulic power unit and the control circuits can be built
to operate on any combination of local voltage. phase or frequency specified.
INTERCONNECTIONS:
The total systems including the barricade(s). hydraulic power unit. control and logic module. control stalions. options and accessories is assembled and tested at Delta before shipment. All hydraulic line connection points and interconnecting hydraulic lines are color coded before shipment. All electrical connection points are clearly marked and cross referenced to the installation manual which accompanies each
system. Connecting cables are not included in most systems unless
ordered as an option.
POWER OFF OPERATION:
The TT207s can be furnished with a special hydraulic pressure circuit which has sufficient reserve capacity to operate the barricade(s) even
with a power failure. The barriers are operated by manually shitting the
control valvels).
EMERGENCY FAST OPERATION:
The barricade system can be equipped with a hydraulic control circuit that permits maximum speed operation of the barricade to the guard position. The speed of operation in this mode depends on the operating condition when the emergency signal is given as well as the length and size of hydraulic lines. etc. ln general the time for full travel will be approximately less than 1.5 seconds.
Control Circuit: Remote Control Panels:
OPTIONS:
CONTROLS:
Key lock switch operation
Remote master control panel with status indication Remote slave (local) control panel (overriden by master) Barrier 'Down too long' annunciation
Radio control operation (any and all functions) High security card readers and cipher pads
Vehicle velocity detection and barrier deployment systems Vehicle direction detection and barrier deployment systems Emergency fast operation
Power off operation and auxiliary emergency fast operation Battery backup control systems
Barrier anti-tamper switches Special voltages
Voltage/phase monitors
Weather resistant electrical enclosures and consoles
Special functions on application (such as interlocks. automatic signal light/gate operation. system status feedback. etc.)
OELTA SCIENTIFIC CORP.:
\ 249m West Avanue SlanIord
Valencia. CA 9l355 Phone: [805) 257-l800 *\ D I I' ' gåtxiagäzzssaroan ' SCIENTIFIC CORPORATION .t EASTEHN REGION: 8303 Arlington Blvd. 1 Suite 7210 i . / Fairfax. VA 2203! Phone:|703)280.2068 '_FAX: [703)'2802083 ENVIRONMENTAL CONTROL Barrier heaters
Hydraulic oil reservoir heaters
Hydraulic oil reservoir coolers fair and water)
Self priming sump pumps Hydraulic power unit enclosures
SAFETY EOUIPMENT
Electrical and hydraulic disconnects
Stop/Go signal lights and brackets Stop/Go signal gate arms
llluminated barrier warning signs and beacons Warning horns
Special paint schemes
Delta Scientific Corp. vehicle safety detectors (inductive loop and I R sensor)
Plus complete design and installation consultation services and worldwide service capability.
UK OFFICE: l. llorlhlield Road Reading. Bark: HGl 8All. England . Phone: 0734 50508) Telex: 8499l0 FAX: 0734 505968 GERMANY: Feldbergstrasse 40 ' 6384 Schmitten-3 West Germany Phone: 06082 865 Telex: 410574
DATA SHEET 1553
SEH'ES TT203
HIGH SECURITY BOLLARD SYSTEMS
HYDHAULIC AND MANUAL
The series TT203 High Security Bollard Systems were developed and are used for intermediate to high security situations. The TT203 Series Bollards have been tested in full scale configuration and they have demonstrated their ability to stop and destroy heavin loaded vehicles. These systems are installed world wide and are protecting entrances that are possible targets ol forced entry. securing high value cargos, protecting storage or warehouse entrances. airport control towers. atomic power generation stations. VIP aircraft and hangers. drug and chemical manufacturing plants. arms storage depots. etc.
The compact size and ease of operation makes this system particularly well suited as a stand alone or a backup of existing pedestrian gates. lt can be installed directly inside of a standard gate and unobtrusively harden an existing entrance against forced entry by vehicles. These systems are supplied either with the Bollards operated by a highly reliable Hydraulic Power Unit for automatic operation or in Manual configuration for low traffic locations. ln either configuration the TT203 Bollards offer the same high degree of protection against forced entry or a suicide bomber. /,
_,
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Hydraulic Bollards can be operated individually or in sets with up to 24 Bollards controlled from a srngle Hydraulic Power Unit.
A wide range of controls. automatic operating sequences. sensors. signals and provisions to protect against extreme environmental conditions are available as options.
DELTA Counter Terrorist Barricades are installed and operating in 130 countries guarding some of the most important facilities in the world.
Delta offers crash rated and crash tested vehicle arrest systems including hydraulic and manual bollards. cable crash beams. sliding and swing gates as well as heavy industrial cantilever rclling gates. gate operators both mechanical and hydraulic. parking gates. passiva tire shredders. velocity and presence vehicle detectors.
Full Engineering, Service and Installation Worldwide
D E LTA SCIENTIFIC CORPORATION
UA 1 A Dutti Tbb'á
SPECIFICATIONS
BOLLARDS
VEHfCLE STUPPING CAPACITY _ rBaserl on frrll scale test re5ults and a theoretical examination of the
rrlatllenlatical model of a truck - bollard colliSlonl
1 Bollard 5.000 pound vehicle (2268 KG) @45 0 MPH (72KPH)
2 Eollards 5 000 p0und vehicle 12268 KGl (<3 500 MPH f81KPH) 3 Bollar ds 5 000 00und vehicle (2268 KGl (43- 54 0 MPH 187KPH)
CONHOURATION
Height 240m 1610mml Body diameter 86m (218mm)
HYDRAULIC BOLLARU SYSTEMS
NUMBER OF BOLLAROS PER SYSTEM _ Up to 24 Bollards can be Operated from the same Hydraulic Power Unit. The system can be conhgured to operate Bollards indrvrduatly or in sets
to meet specrfrc security requirements.
OPERATlNG TIME:
The operatrng speed is field adjustable in the range of 2.5 to 15 seconds.
ORlVE CONFIGURATION: _ Each Bollard rs posrtroned by means of a precrsion hydraulic cylinder. HYORAULIC POWER SYSTEM:
The hydraulic power system is a self contained source of hydraulic power to Operate one 0r more bollards either srmultaneously or in sets. The components which constitute the system have been caretully selected for then function. long life. availabrlity and dependability. The system rs deSrgned and will provide precisely controlled power to the bollat'dlSl on a reliable basrs day in and day out. year in and year out wrth a minimum of attention or maintenance. The hydraulic power unit Stands alone and can be located wrthin 1501eet (457m) of the bollards.
For distances over 50 leet (15.2ml the hydraulic line size may be
increased to marntain the operatrng speeds).
OPERATlNO VOLTAGE/POWER CONSUMPTION: Hydraulic Power Unit 3 HP (22 Kw) (sm unit)
208-230/460 VAC - 3 PH - 60 HZ 220/380/440 VAC - 3 PH- 50 HZ Single phase available on request 50 VA * 60 VA per bollard or set
115/230 VAC - 1 PH - 50/60 HZ 50 VA
24 VAC (Std). 24 VOC (Optional)
Note: Both the hydraulic power unit and control Circuits can be built to operate on any combination of local voltage. phase or frequency specified.
INTERCONNECTIONS: _ _ The total system including the bollardts) hydraulic power unit. control
and logic module. control stations. options and accessories is
assembled and tested at Delta belore shipment. All hydraulic fine connection pornts and interconnecting hydraulic lines are color coded before shipment. All electrical connection points are clearly marked and cross referenced to the installation manual which accompanies each system. Electric interconnecting cables are not included in most
systems unless ordered as an option. POWER OFF OPERATION:
The TT203 can be furnished with a special hydraulic pressure circuit
which has sufticrent reserve capacity to operate the bollardlsl even with
a power failure. The bollards are operated by manually shitting the control valvefs).
EMERGENCY FAST OPERATION:
The bollard system can be equipped with a hydraulic control circuit that permits maximum speed operation of the bollards to the guard position. The speed of operation in this mode depends on the operating condition
when the emergency signal is given as well as the number of bollards. length and size of hydraulic lines. etc. DELTA Engineering will provide detail information for specific srte conditions.
ln general the Emergency Fast Operation speed is less than 2.0seconds.
Control Circurl_ Remote Control Panels
OPTIONS:
[Manual system]The Manual Configuration of the TT203 is deployed to the guard position by lrlting the Bollard into posrtion by means of a handle in the top of the unit The weight of the Bollard. which is substantial. is counterbalanced by means of a patented system. The force required to deploy the Bollard is under 40 poonds In the full up position and the full down position the bollard rs prnned by a spring actuated plunger. A hasp is provided to secure the Bollard in either position .with a padlock (not furnished). HYORAULIC BOLLARO SYSTEM . Options:
Controls
Key lock swrtch operation
Remote master control panel with status indication Remote stave (local) control panel (overrrdden by master)
Bollard 'Down too long' annunciation
Radio control operation tany and all functions) High security card readers and cipher pads
Vehrcle velocny detection and bollard deployment systems Vehicle direction detection and bollard deployment systems Emergency fast operation
Power of operation and auxrtiary emergency fast operation Battery backup control systems
Botlard antr-taper swrtches SpeCial voltages
Voltage/phase monitors
Weather resistant electrical enclosures and consoles
Special functions on application (such as interlocks. automatic signal light/gate operation. system status feedback. etc.)
Environmental Control Bollard heaters
Hydraulic oil reservoir heaters
Hydraulic oil reservoir coolers fair and water)
Self priming sump pumps
Hydraulic power unit enclosures
Safety Equipment
Electrical and hydraulic disconnects Stop/Go signal lights and brackets Stop/Go signal gate arms
tlluminated warning signs and beacons Warning horns
Special paint schemes
Vehicle salety detectors (inductive loop and l-R sensor)
Plus complete design and installation consultation services and
worldwide service capability.
DELTA SCIENTIFIC CORPORATION 24901 West Avenue Stanford Valencra. CA 91355 Phone: (805) 257- 1800 Telex 704283 FAX: (805) 257-0617
DELTA
SCIENTlFlC CORP.EASTERN REGIONAL OFFICE U.K. OFFICE [LONDON] FRANKFURT OFFTCE 8303 Arlington Blvd. 1. Northfreld Road Bockenheimer Landstrasse 98-100
Surte 210 Reading. Berks 6000 Frankfurt, AM Main 1 Fairfax. VA 22031 201 BAH. England west Germany
hone: 0734 505081 '
Phone: (703) 2802068 Telex: 849910 :gi-3:13:22?
FAX: (703) 2802083 FAX; 0734 505968 ;Axbsgu 5436
'DATA SHEET 1556 SERlES TT212
"
CBASH BATEB CABLE BEAM BABBIEB
HYDBAULIC AND MANUAL 0PEBAT|BN
This series of CRASH RATED BARRIERS is designed for MEDIUM SECURITY applications. This generally is a case where the attack vehicle is traveling at aspeed of less than 25 MPH (40 KPH) at the time of impact and weighs less than 10.000 LBS. (4.536 KG).
A frequent use is in SALLY PORT or lNSPECTlON PORT applications. The TT212 is used as the secondary control backing for a heavier barricade which is the first line of protection. The first _ barricade forces a vehicle to come to a full stop before entering the port, the TT212 prevents the vehicle in the port from leaving until authorized.
Other applications include closing off restricted or reserved parking areas, impound yards, freight terminals. storage and warehouse entrances. arms storage depots, inspection points, shipping and receiving docks. emergency lanes. and other locations where standard traffic controls or gates are not capable of resisting creash forces or vandalism.
The TT212 SERIES CABLE CRASH BEAM BARRIERS have been successfully tested in full scale configuration and they have demonstrated their ability to stop heavily loaded vehicles. Light weight. simple installation. compact design, and ease of operation makes these system particularly well suited for stand alone or backup applications. They can be installed directly inside of standard gates and unobtrusively harden an existing entrance against forced entry by vehicle.
These systems are available either operated by a highly reliable Hydraulic Power Unit for automatic operation or in Manual configuration. ln either configuration they offer the same high degree of protection.
In the Hydraulic configuration a wide range of controls. automatic operating sequences, sensors. signals and provisions to protect against extreme environmental conditions are available as options.
DELTA Counter Terrorist Barricades are installed and operating in 130 countries guarding some of the most Important facrlities in the world.
_Delta offers crash rated and crash tested vehicle arrest systems including hydraulic and manual boilards. cable crash beams. sliding and swing gates as well as heavy industrial cantilever rolling gates. gate operaturs both mechanical and hydraulic. parking gates. passive tire shredders. velocity and presence vehicle detectors.
Full Engineering, Service and Installation Worldwide
D E LTA SCIENTIFIC CORPORATION
FIGURE 3. CRASH RATED CABLE BEAM BARRIER 8
UHIA DHttl 1:030
SPECIFICATIDNS [General]
ARRESTING CAPACITY
Based on a lull scale crash test of the TT212 and the analysis of the mathematical model of the collrsion. the arresling capacity ot both the manual and the hydraulic versions of the TT212 is 243.000 FT-LBS (329.500 JOULES).
This rs eourvalent to the energy of a 10.000LBS (4.536KG) vehicle
movrng at 27 MPH (44 KPH) or of a 6.000 LBS (2.272 KG)
automobile travelrng at 35 MPH (56 KPH). NEIGHT:
The height above the roadway at whichthe CABLE CRASH BEAM
rs located is optional and depends on the specific traffic and
threat conditions. ln most situations a height of between 30
inches (762 MM) and 36 inches (914 MM) provides the best protection. DELTA engineering will make specrfic recommendations based on site requirements.
LENGTH
Free openings of up to 20.0 FEET (6.1M). MOUNTING
The Cable Crash Beam Barrier is mounted on concerete bollards
which are cast in situ.
SPECIFICATIONS [Hydraulic]
OPERATION
The system can be raised or towered in 8 to 15 seconds (customer adjustable) and is controlled from one or more master and slave panels. The Barricade direction is instantly reversrble at any point in its cycle.
DRIVE CONFIGURATION
The Hydraulic Cable Crash Beam is positioned by means of a
precision hydraulic cylinder.
HYORAULIC POWER SYSTEM:
The hydraulic power system is a self contained source of hydraulic power to operate one or more barriers either simultaneously or in sets. The components which constitute the system have been carefully selected for their lunction. long life. availability and dependability.
The system is designed and will provide precisely controlled
power to the barrier(s) on a reliable basis day in and day out.
year in and year out with a minimum of attention or maintenance. The hydraulic power unit stands alone and can be
located within 150 1681 (45.7m). For distances over 50 feet (15.2m), the hydraulic line srze may berncreased to maintain the operating speed.
OPERATING VOLTAGE/POWER CONSUMPTION
Hydraulic Power Unit: 1 HP (.75 KW) (Std unit)
208-230/460 VAC - 3 PH - 60 HZ 220/380/440 VAC - 3 PH - 50 HZ Single phase available on request 50 VA + 40 VA per barrier 115/230 VAC -'1 PH - 50/60 HZ Remote Control Panels: 50 VA
24 VAC (Std) 24 VDC (Optional)
NOTE: Both the hydraulic power unit and the control circuits can
be built to operate on any combination of local voltage. phase or frequency specified operating speeds.
INTERCONNECTIONS:
The total systern including the hydraulic power unit. control and
Iogic module. control stations. Options and accessories is assembled and tested at Delta before shipment. All hydraulic
line connection points and interconnecting hydraulic lines are color coded before shipment. All electrical connection points are clearly marked and cross relerenced to the installation manual
which accompanies each system. Electric interconnecting
cables are not included in most systems unless ordered as an opbon.
POWER OFF OPERATION:
The TT212 can be lurnished with a special hydraulic pressure
circuit which has suflicient reserve capacity to operated the barrier(s) even with a power failure. The system(s) in this mode operated by manually shitting the control valve(s).
SPECIFICATION (Manual)
OPERATION
The manual Configuration of the TT212 is counterbalanced to operate with minimal force required. Both the up and the down
(guard) positions are cushioned by means of high strength
torsion springs. The barrier will stay in either the full up or down position.
MANUAL LOCKING
The barrier is supplied with a latch and padlock hasp for securing the barrier in the down position.
Control Circuit:
OPTIONS: [Partial Listing)
CONTROLS (Hydraulic)
Remote master control panel with status indication Remote slave (local) control panel (overridden by master) Radio control operation (any and all functions)
High security card readers and crpher pads Power off operation
Battery backup control systems Anti-tamper swrtches
Special voltages
ENVIRONMENTAL CONTROL
Hydraulic oil reservoir heaters & coolers Hydraulic power unit enclosures
SAFETY EOUIPMENT
Stop/Go signal lights and brackets
Special paint schemes
Vehicle safety detectors (inductive loop and l-R sensor) Plus complete design and installation consultation services and worldwide service capability.
DELTA SCIENTIFIC CORPORATION EASTERN REGIONAL OFFICE U.K. OFFICE [LONDON] FRANKFURT OFFICE 24901 West Avenue Stanlord 8303 Arlington Blvd.
Valencia. CA 91355 Suite 210 Fairfax. VA 22031
Phone: (805) 2574800
1. Northtield Road Bockenheimer Landstrasse 98-100
Reading. Berks 5000 Franldun, AM Main 1 RGl 8Al-l. England west Germany
Phone: 0734 505081 .
'men 849910 Phone. 06974 6110
Telex: 704283 Phone: (703) 2802058 TeIeX'4175850
D E L_ | A FAX; (805) 257-0617 FAX: (703)2802083 FAX: 0734505968 mamma SCIENTIFIC CORP.
FIGURE 3. CRASH RATED CABLE BEAM BARRIER (i) (continued)
mechanical systems would cost 75,000 to 125,000 USD. The design in Figure 3
would cost somewhat less.
Use of Energy-Absorbinq Barriers
Based on a review of candidate energy-absorbing barrier designs, it is the
authors' opinion that at least two systems are worthy of further study. These
are the "arrestor net" system mentioned previously and the "mobile inertia barrier" system. Conceptual drawings of these systems are contained in Figures'
4 through 8. As discussed previously, the arrestor net design has been crash
tested and evaluated at TTI. The inertia barrier concept has been tested and has
been very successfully used in the USA, and other countries, as a permanent crash
cushion to shield roadside hazards. 1
In the arrestor net system energy is dissipated by pulling a metal strap through a series of roller-benders. Spacing of the rollers and the cross-section of the metal strap can be adjusted to obtain a specified tensile pull force. When in the stored position the net would be raised to a height sufficient for vehicle clearance. In the deployed position the net would be lowered and engaged
with a mechanism which in turn would be engaged with the metal strap. It is
believed that the system could also be designed to function as a swinging gate, where two swinging gates would meet in the center of the road and interlocked. Note that it may be desirable to shield the rigid support structure for the metal
bender with a crash cushion, as shown in Figure 6. It could also be shielded
with conventional guardrail.
The mobile inertia barrier system dissipates energy through momentum transfer. The sand tub modules would be placed on a low-profile, wheeled dolly, which in turn would be supported on tracks for movement to the deployed position. A computer program was written and used for the arrestor net design to
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evaluate effects of key system parameters on occupant risk factors. Key
parameters include tensile pull force of the metal strap, road width (or distance
between benders), mass of impacting vehicle, and speed of impacting vehicle. A
study of key parameters of the inertia barrier design was also made using basic principles of mechanics.
Figures 9 through 14 contain results of the parametric study of the
arrestor net system. Figures 9 and 10 show how the occupant impact velocity
(01V) varies as a function of the road width (or distance between benders) for (a) an impact speed of 70 km/hr, (b) vehicle masses of 816 kg and 2041 kg, and
(c) an effective tensile pull force of 56 kN and 111 kN. Note that the
recommended limit on 01V is 12 m/sec (1). It was assumed that the vehicle
impacted the center of the net. Figures 11 and 12 show how the maximum vehicular
deceleration varies as a function of the same parameters. Note that the
recommended limit on occupant ridedown acceleration (measured as the highest 10
millisecond average) is 20 g's (l). Figures 13 and 14 show how the stopping
distance of the vehicle varies as a function of the same parameters. Based on
this preliminary evaluation, the arrestor net appears to have desirable Characteristics, i.e., it could safely stop a 2,040 kg vehicle and a 816 kg
vehicle at 70 km/hr, within a stopping distance of approximately 8 m or less, depending on the roadway width and the tensile pull force of the metal strap.
It is estimated that this system could be installed at a cost of 40,000 to 60,000 USD.
Table 1 shows the estimated occupant risk parameters for the mobile inertia barrier. Note that these values were computed for two assumed impact positions
of the vehicle, as shown in Figure 15. Note the occupant risk parameters are
below recommended limits (1). Also note that the design is approximately 5.5 m
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@ TI S: "T ES I;approximateiy 7.5 m. It is estimated that this system could be instaiied at a cost of 50,000 to 75,000 USD.
Mmm
Based on preliminary evaluations mobiie barriers for raiiroad crossings
appear feasibie and worthy of further study. Two types of barriers should be
considered, nameiy, rigidznuienergy absorbing designs. DependingCNiextenuating
circumstances, one of the two types may be warranted.
If a rigid barrier is warranted it is beiieved that current technoiogy in the area of security barriers is such that existing designs could be quickiy
adopted for raiiroad crossings. Figures 1 through 3 show three such barriers.
It is estimated that a typica] barrier system using designs of this type couid be instaiied for a cost of 75,000 to 125,000 USD.
If an energy-absorbing barrier is warranted it is beiieved that there are
at 1east two concepts that show promise. These are the arrestor net design, as
iiiustrated in Figures 4 through 6, and the inertia barrier design as i11ustrated
in Figures 7 and 8. It is estimated that a typica] barrier system using the
arrestor net design couid be instaiied for a cost of 40,000 to 60,000 USD. It
is estimated that a typicai barrier system using the inertia barrier design couid
be instaiied for a cost of 50,000 to 75,000 USD. Of these two designs, the
arrestor net design is probabiy the most feasibie.
