Crash

Now, I have covered passive safety previously, but this week, the subject was brought back into my mind as I happened across the aftermath of a crash as I was out on my regular pootle.

I obviously don't know the circumstances, but I saw a car sat on the verge next to a 50mph section of the A12 in east of London. That's not always a rarity given how often I see people parked in places like this, but it was a section with no houses and so looked out of place.

As I approached, it became clear from the tyre marks in the verge that the vehicle had been driven off the road and it had been stopped by a tree.

It's a stark scene which shows how immovable even a smallish tree is as well as the apparent crash-worthiness of a modern car. It's hard to see, but as well as driver and passenger air bags, side air bags had also been deployed. As I say, I don't know the circumstances of the crash, but it is a reasonable assumption that the occupants will have walked away from it.

From a sustainable safety point of view, we are interested in protecting people, even if they have poor judgement or make mistakes and so regardless of the actual cause here, the presence of trees so close to the carriageway is a risk whereas the crash-protection measures within the vehicle compensates.

This is a high-speed road built decades ago and frontage activity varies greatly. By modern standards, large trees close to a carriageway is something which would be avoided, or there would be sections of crash barrier protecting drivers from denser groups of trees. A process of risk management would be used to decide whether or trees in positions like this should be removed. The problem here is many sections of this road doesn't have large verges and in many cases, people outside of the motor vehicles are walking and cycling right next to the carriageway.

The UK has many legacy roads likes this where towns and cities grew next to key routes. Because we have decided at a policy level to maintain road transport as the priority, many of this roads were dualled over time and so we have the uncomfortable problem of important traffic corridors passing through communities. Maintaining traffic flow on old roads to modern trunk road standards are incompatible with people needing to traverse them.

This crash is a legacy of this. Although on the face of it, the high speed traffic is isolated from both oncoming traffic and those outside of the motor vehicles, it's just an illusion. Most of these roads cannot easily be rebuilt to modern standards of geometry and crash-worthiness and there aren't any ways of bypassing them (unless we destroy the neighbourhoods they sever).

It's a hard one to deal with because these are roads designed for speed and in the absence of enforced speed limits, they are to laid out in geometries within which many people will be happy to put their foot down. About the only options we have is to maybe narrow the lanes a touch and drop the speed limits and perhaps more realistically, enforce those lower speed limits with average speed cameras which in themselves is a longer term liability in terms of cost if compliance is good. Hopefully one day the existing speed limiters in new cars will be on all the time.