Vehicle Restrain Systems for Roadways
The most important safety problems on roadways are:
- uncontrolled veering off the roadway.
- Impact with vehicles and obstacles along the roadway such as trees. posts. masts and traffic signs.
- falling from bridges and down embankments.
In Europe. up to 40 % of fatal traffic accidents are caused by vehicles diverging from
the roadway due to e.g. not adhering to the speed limits. abuse of alcohol, inexperience of the road user or inappropriate Infrastructure.
The number of motorised vehicles and the associated private and commercial
mileage are continuously increasing in the European Union. The number of
accidents, as well as traffic fatalities, are decreasing which is also due to the intense development of passive safety through steel safety barriers installations.
Passive Safety Barriers (guard rails) are installed at the verge or in the median
between traffic lanes in order to prevent errant vehicles from leaving the road and colliding with objects or oncoming traffic.
Safety barriers are defined as deflective or absorptive according to their function.
Their reaction on impact determines if they are a deformable or a rigid system.
Development of roadsafety
The development of deflective safety barriers on roads actually goes back to the time when motor vehicles were first introduced to road traffic.
The then unknown round A-Profile (from ARMCO-Flex-Beam). also known as W Beam and the B-Profile with corners (Bethlehem-Safety Beam) were already used in the USA in the 40s. They are still in use and equal to steel safety barrier systems on roads. having proven themselves nationally and internationally.
Deformable steel safety barrier systems were first used in the middle of the 50s an dintroduced to Germany from the USA by PASSCO.
The early steel systems were very rigid (with IPE 140mm Posts) and. in competition with concrete. wire rope. fencing and other systems in the 60s. were further developed and analysed through crash tests and optimised.
To-days deformable steel safety barrier systems (with Sigma 100mm posts) have proven themselves as standard safety solutions for roads both from technical as well as commercial aspects. Because of their many advantages. it was possible to further develop the systems to optimise road safety on verges.
When one talks about passive road safety installations in Europe. we mean the well known steel Safety Barriers Systems.
To-days steel safety barriers systems are capable of absorbing an errant vehicle, reduce excessive speed on impact and contain the vehicle at the edge of the roadway.
Basically, steel is the ideal material for absorbing energy in accidents and provides adequate protection for passengers through elastic and knead able deformation.
The advantages of steel safety barriers systems are their quick installation and dismantling. flexible adaptation to local ground conditions and being a simple solution to different safety requirements.
The PASSCO steel safety barriers systems consist of a continuous steel system. At the same Installation height (0.75 m). steel safety barrier beams are connected
horizontally and strengthened with vertical posts and/or construction parts in order to achieve different restraining or containment levels.
Steel safety barriers installations can be flexibly adapted to local safety requirements by specific post spacing and the fitting of construction parts (such as spacer elements) as well as minimum installation lengths. The respective requirements of the European Norm EN1317 can therefore be met individually.
Research conducted by the Federal Department for Road Traffic (BAST) according to EN1317. showed that single sided systems perform better overall than double sided systems. In medians. they particularly have an advantage when there are different
heights between the traffic lanes. They can be adapted to suit the installation height required for the respective traffic lane which is very important to ensure proper function. A further advantage is repairing impact damage which can be undertaken
without affecting the other traffic lane. In addition. the second system provides further safety if the first system is breached. Among other things. the height of the second system can be increased if the vehicle is re-directed by a simple change at the back of the system.
A very positive finding from all the tests conducted by BAST is that on impact. the longitudinal forces on the steel assemblies. which primarily have to be absorbed by the horizontal beams and their connections. are significantly absorbed by all of the
component parts. Furthermore. in all of the tests on the safety barriers installations, the impact force values are better than ASI = A.
Note: If an alternative Vehicle Restrain System is available. then the system with the lower ASI value is preferred.
The European Norm EN1317 for Vehicle Restrain Systems should provide road users throughout the European Community the same safety standard on roads when travelling from one European country to another.
The frequency of repairs and renewals are silent witness to the need for functional passive safety installations. Statistics have proven that they have contributed considerably to road safety in Europe and reduced the severity of accidents as well as saving many lives.
There is further potential in the improvement of Restrain Systems an roadways e.g. with Crash Cushions. Approach/Departure Terminals and tree safety systems.
An improvement in traffic safety can also be achieved by coordinating, for example. road markings, signage and road works safety installations.