Advanced Driving Hub

So Peter Rodger from IAM RoadSmart and Edmund King from the AA was just on BBC R4 'PM' program discussing Smart Motorways. https://www.bbc.co.uk/sounds/play/m000281y 48 mins in.

Edmund said the M42 (the original smart motorway) has safety refuges every 600-800 yards but subsequent motorways are much more spread out - 2.5km or 1.5m.

What do people here think of Smart Motorways?

It would be "smarter" to get drivers off the roads who can't follow correct lane discipline.

jont- wrote:It would be "smarter" to get drivers off the roads who can't follow correct lane discipline.

The main point raised during the interviews was the relatively long gap between safety refuges on newer Smart Motorways. I've put a link in the original post so people can listen if they wish.

I think I remember figures from Highways England on Radio4 recently and they showed that the accident rate on "smart" motorways is higher than on traditional variety ?

I think they are a fantastically expensive solution looking for a problem.

Strangely Brown wrote:I think they are a fantastically expensive solution looking for a problem.

They're a way of adding lane capacity, with the enforced variable speed limits reduce speeds to improve the time separation between vehicles.

If you can suggest another way of achieving those aims without using additional land alongside the carriageway (in some places that's simply not possible), then speak up!

Remove traffic by removing drivers who don’t deserve their licence.

Tongue only partly in cheek.

Horse wrote:They're a way of adding lane capacity, with the enforced variable speed limits reduce speeds to improve the time separation between vehicles.

Do the variable speed limits achieve that, though? Or, more precisely, does the way they are enforced achieve that?

Behaviour I have observed includes:
- drivers failing to use lane 1 of 4 altogether (so I can use it and sail past hundreds)
- assuming the enforcement cameras are active even when no limit is displayed on the gantries - or just panic braking in response to distance markings on the road!
- ignoring displayed limits (perhaps in hired vehicles or others whose drivers believe they will not be summonsed)

I adopt a "burn and coast" approach to try to maximise progress - I'll move to lane n, drive between the gantries at an indicated 70 - 75, then lift to meet the posted limit at each point of possible enforcement. That this option is left open seems to me to undermine the idea behind the scheme altogether. Why is there not average speed enforcement?

Does anyone know where I can find data on prosecutions for exceeding smart motorway temporary speed limits?

David

kfae8959 wrote:[...I adopt a "burn and coast" approach to try to maximise progress - I'll move to lane n, drive between the gantries at an indicated 70 - 75, then lift to meet the posted limit at each point of possible enforcement. That this option is left open seems to me to undermine the idea behind the scheme altogether. Why is there not average speed enforcement?

Smart motorways often have average speed cameras...your 'burn and coast' method could still trigger them.

Does anyone know where I can find data on prosecutions for exceeding smart motorway temporary speed limits?

I know many thousands of motorists have been prosecuted (or offered an education course) for exceeding the smart motorway limits...a quick google showed individual prosecutions but there must be a summary somewhere.

kfae8959 wrote:

Horse wrote:They're a way of adding lane capacity, with the enforced variable speed limits reduce speeds to improve the time separation between vehicles.

Do the variable speed limits achieve that, though? Or, more precisely, does the way they are enforced achieve that?

Enforcement won't change actual behaviour at the moment that it's taking place, it's the compliance (or fear of being caught) that makes the difference.

That compliance will only be for the number of vehicles on that stretch of road at that time, which will have a direct relationship to the physical separation distance between them. Slower speeds will result in a longer time interval between the vehicles, so ought to be safer (time to react, shorter braking distances).

Lower speeds might also reduce bunching and potentially acceleration and braking, such as:


Also (although AFAIK it's not being done at the moment), there may be benefits from enforced lower speed limits on reducing air pollution.

martine wrote:Smart motorways often have average speed cameras...

Which ones?

David