Arrestor Beds and Road Safety
Do you know what is an arrestor bed? A definition found on the internet describes an arrestor bed as “an area of a special material designed to stop a runaway vehicle. Arrestor beds include Engineered materials arrestor system, crushable concrete used to stop aircraft which overrun a runway. Runaway truck ramps on highways. Railway safety sidings.”
We decided to approach SANRAL and gain more insights on the arrestor beds we find next to the roads in South Africa:
How many of these arrestor beds can be found across South Africa along our national roads and where can they mostly be found?
There are much spread across the country. They are mostly found where the risk of runaway heavy vehicles is high i.e. in steep terrain, prior to tight bends and on approaches to toll plazas.
Are you aware of any arrestor beds along roads not managed and maintained by SANRAL?
Yes. The Provincial Departments of Transport operate and maintain arrestor beds on their road network.
What would you describe as the primary purpose of these arrestor beds?
To allow vehicles (mostly heavy vehicles) who are unable to reduce their speed and area of refuge, where can come to a safe stop away from other traffic despite a braking mechanism (or other) failure.
What are the main structural features of an effective arrestor bed?
They must be designed to the correct length and depth to allow effective arresting of runaway heavy vehicles given the site-specific road geometry. An anchor block is generally required for winching out the heavy vehicles once they have come to a safe stop.
What are the most important compounds/mixtures to be found in arrestor beds - do all of the arrestor beds in SA and managed by SANRAL have to meet the same design and compound features?
Single sized marble-like aggregate (commonly referred to as pea gravel) that is kept free of fine material and other contaminants. The aggregate must have a high crush resistance as crushing would release fines and result in the arrestor bed material compacting.
Once compacted it would no longer effectively perform its arrestor function. The material is specified to meet the same technical requirements in SANRAL’s maintenance specifications.
Are they meant for all types of vehicles that find themselves in difficulty?
They are chiefly put in place to arrest runaway heavy vehicles, but all vehicle types requiring safe arresting can use them.
Are there specific protocols for the removal of vehicles from an arrestor bed and compliance requirements before they can be used again?
There are no specific removal protocols. The arrestor bed material is ‘fluffed’ once a month and after every vehicle entry.
Is there a charge/financial penalty for the usage by and removal of vehicles from an arrestor bed?
There is no financial penalty. The only charge passed on to the vehicle owner is the towing cost for removing the vehicle from the arrestor bed.
Any misconceptions among the public in respect of info they need to know about arrestor beds?
If in difficulty and unable to stop using the arrestor bed. Do not bypass it and attempt to control the vehicle instead. Many severe crashes could be avoided by following these simple guidelines.
I also recall attending a SAICE lecture (also about 20y ago) on the importance of a compulsory stop for all HVs (Eeufees Road Pretoria was the case study) in advance of the arrestor bed - i.e... stop on the crest before a long downhill, check brakes and if not worn, proceed, else remain in place or use the first arrestor bed on the downgrade, and wait for relief.