Smart motorways are (not) more dangerous

[nekomatic]

First stat that jumps out is live lane breakdowns (where the driver is not able to get to the hard shoulder on a traditional motorway or not able get to a refuge/layby in an all lane running one). About 20% for trad motorway, about 38% for smart motorways. Not good.

On a motorway with light traffic, few breakdowns will be live lane breakdowns as vehicles will usually be in the left lane, or able to move left when the breakdown happens. On a congested motorway that won’t be the case. The motorways that have been upgraded to all lane running are of course the ones that were most congested. Is that taken into account anywhere?

[Martin Y]

First stat that jumps out is live lane breakdowns (where the driver is not able to get to the hard shoulder on a traditional motorway or not able get to a refuge/layby in an all lane running one). About 20% for trad motorway, about 38% for smart motorways. Not good.

On a motorway with light traffic, few breakdowns will be live lane breakdowns as vehicles will usually be in the left lane, or able to move left when the breakdown happens. On a congested motorway that won’t be the case. The motorways that have been upgraded to all lane running are of course the ones that were most congested. Is that taken into account anywhere?

Doesn't seem so but that's a good point - the sections chosen for conversion to ALR will not be typical.

[Sciolus]

Reasons why ALR motorways are different include:
- More vehicles, at least in peak times;
- Four lanes, so possibly less congestion overall;
- Speed control, leading to fewer high speeds and most traffic travelling at similar speeds (hence fewer lane changes etc.);
- Reactive speed control, with lower speeds during very busy periods (I think);
- Anything else?

Speed control will tend to reduce moving collisions*. It's not obvious that any of those differerences will help appreciably with break-down collisions.

*But ALR isn't a prerequisite for that.

[Martin Y]

In the "anything else" category is monitoring for breakdowns (almost all by cameras when it's supposed to be by fancy radar) so breakdowns get noticed sooner (17 mins vs 20-ish mins was it?). That should mean a live lane stranded vehicle is vulnerable for less time on that type of motorway.

[tenchboy]

Update

[dyqik]

Update

I can't see any new evidence there at all. Just know-nothing crap like statements that the safety review "was just a paperwork exercise and a PR exercise."

Yes, of course the safety review was a paperwork exercise. That's how you do safety reviews, on paper/documentation. You don't do them with hammers.

[plodder]

One problem here is that non-smart motorways are also stupidly dangerous.

[shpalman]

One problem here is that non-smart motorways are also stupidly dangerous.

Less dangerous than normal roads.

[plodder]

Normal roads are crazy dangerous. It's hard enough to eyeball risk, but when the baseline is so high things get really tricky. The risk profiles change dramatically on different roads as well. You're in less danger if you break down and pull over on a suburban road than on a smart motorway, that's for sure. And this element of the risk profile is what the OP is about.

[shpalman]

Facts on road fatalities

In 2013, there were 1713 reported road fatalities which corresponds to about half a week's worth of covid deaths in November 2020.

Fatalities on motorways account for less than 10 per cent of reported road deaths. Between 2009 and 2013 motorways carried around 20 per cent of GB traffic, but accounted for just 6 per cent of road deaths. Mile per mile, the risk of death on motorways was around 5 times lower than the equivalent figure for rural roads and 3 times lower than for urban roads.

Motorways are statistically the safest roads in GB. They are built and maintained to higher design standards than other roads on the network, including having wider lanes, grade separated junctions and each carriageway is separated by barriers of both steel and concrete in order to improve safety and avoid the risk of head on collisions. Motorways include greater use of technology to manage the flow of traffic and variable speeds which contribute to the strong safety record.

In the last five years car occupants made up the majority of fatalities (56 per cent) and the majority of motor traffic (80 per cent) on motorways. Pedestrians* accounted for 17 per cent of road deaths on motorways while goods vehicles and motorcyclists accounted for 25 per cent collectively.

* - Although pedestrians and pedal cyclists are not allowed on motorways as a matter of course, people can make mistakes and enter the motorway by error or deliberate act, or can become pedestrians if they have to exit a broken down vehicle.

[Martin Y]

Although ordinary roads carry a much higher risk of your getting into an accident, and a fatal accident too, the thing which makes smart motorways scary is that if something goes wrong - a breakdown or minor accident - and leaves you stranded, you are in a very frightening situation at serious risk of getting killed. c.f. Fear of flying. The absolute risk may be lower than alternatives but humans don't like the thought that if something goes wrong you have no control and there's f.ck all you can do.

[shpalman]

Although ordinary roads carry a much higher risk of your getting into an accident, and a fatal accident too, the thing which makes smart motorways scary is that if something goes wrong - a breakdown or minor accident - and leaves you stranded, you are in a very frightening situation at serious risk of getting killed. c.f. Fear of flying. The absolute risk may be lower than alternatives but humans don't like the thought that if something goes wrong you have no control and there's f.ck all you can do.

So they're not actually more dangerous, people just feel like they are?

[Martin Y]

So they're not actually more dangerous, people just feel like they are?

They're a much less dangerous kind of road to drive on.
They're a much more dangerous kind of road to break down on.

It depends on what sort of accident you plan to have.

[shpalman]

Somebody bring some stats or we'll just be wot I reckoning at each other for the rest of the life of the universe.

[dyqik]

Somebody bring some stats or we'll just be wot I reckoning at each other for the rest of the life of the universe.

That would be a pointless paperwork exercise, though.

[Bird on a Fire]

Are stats really necessary to support the idea that it's relatively dangerous (not to mention terrifying) to break down on a motorway with no hard shoulder?

[Sciolus]

They're necessary if you want to do a risk-benefit analysis and decide what should be done about them.

The main advantage of smart motorways is you can shovel more cars through, and they're much cheaper and get less public scrutiny (and protest) to build than widening the carriageway. (They were dreamt up at the height of opposition to new road-building works as a way of pretending they weren't building more roads.) Is that sufficient benefit for the extra risk? HE (or whatever they're called this week) argue that the extra safety measures associated with smart motorways offset the extra risk of not having a hard shoulder, ignoring the fact that you can have the extra safety measures *and* a hard shoulder.

[satire]Although since hardly anyone uses the new lane anyway, you can park there in perfect safety most of the time. If they wanted to increase capacity, they should have added an extra lane on the right not on the left.[/satire]

[shpalman]

[satire]Although since hardly anyone uses the new lane anyway, you can park there in perfect safety most of the time. If they wanted to increase capacity, they should have added an extra lane on the right not on the left.[/satire]

I noticed this when the Como-Milan* motorway got widened from 2 lanes to 3 and on the first trip down it my ex-father-in-law did the whole thing in the middle lane.

[Fishnut]

They're necessary if you want to do a risk-benefit analysis and decide what should be done about them.

The main advantage of smart motorways is you can shovel more cars through, and they're much cheaper and get less public scrutiny (and protest) to build than widening the carriageway. (They were dreamt up at the height of opposition to new road-building works as a way of pretending they weren't building more roads.) Is that sufficient benefit for the extra risk? HE (or whatever they're called this week) argue that the extra safety measures associated with smart motorways offset the extra risk of not having a hard shoulder, ignoring the fact that you can have the extra safety measures *and* a hard shoulder. [my emphasis]

[satire]Although since hardly anyone uses the new lane anyway, you can park there in perfect safety most of the time. If they wanted to increase capacity, they should have added an extra lane on the right not on the left.[/satire]

Is this an advantage though? Do we want more cars being shovelled through? At a time when we're trying to reduce carbon emissions, getting people out of cars rather than making things easier for them would seem to be the sensible course of action. And there's decades of evidence that if you build more road capacity people just make more trips - a phenomenon called "induced traffic". The Campaign for Better Transport has some useful UK-specific data.

[Millennie Al]

And there's decades of evidence that if you build more road capacity people just make more trips - a phenomenon called "induced traffic". The Campaign for Better Transport has some useful UK-specific data.

Does that work for other modes of transport - buses and trains - or just private vehicles?

[shpalman]

And there's decades of evidence that if you build more road capacity people just make more trips - a phenomenon called "induced traffic". The Campaign for Better Transport has some useful UK-specific data.

Does that work for other modes of transport - buses and trains - or just private vehicles?

I don't know, does it?

[snoozeofreason]

And there's decades of evidence that if you build more road capacity people just make more trips - a phenomenon called "induced traffic". The Campaign for Better Transport has some useful UK-specific data.

Does that work for other modes of transport - buses and trains - or just private vehicles?

I don't know, does it?

There seems to be a fair bit of research on vicious and virtuous cycles in the context of buses. As far as I can make out it confirms what common sense would suggest - that if bus services are more frequent more people use them, and vice versa. This paper is on modelling of the virtuous cycles, but it contains links to some of the empirical evidence (none of which I have had the time to chase up).

[dyqik]

They're necessary if you want to do a risk-benefit analysis and decide what should be done about them.

The main advantage of smart motorways is you can shovel more cars through, and they're much cheaper and get less public scrutiny (and protest) to build than widening the carriageway. (They were dreamt up at the height of opposition to new road-building works as a way of pretending they weren't building more roads.) Is that sufficient benefit for the extra risk? HE (or whatever they're called this week) argue that the extra safety measures associated with smart motorways offset the extra risk of not having a hard shoulder, ignoring the fact that you can have the extra safety measures *and* a hard shoulder. [my emphasis]

[satire]Although since hardly anyone uses the new lane anyway, you can park there in perfect safety most of the time. If they wanted to increase capacity, they should have added an extra lane on the right not on the left.[/satire]

Is this an advantage though? Do we want more cars being shovelled through? At a time when we're trying to reduce carbon emissions, getting people out of cars rather than making things easier for them would seem to be the sensible course of action. And there's decades of evidence that if you build more road capacity people just make more trips - a phenomenon called "induced traffic". The Campaign for Better Transport has some useful UK-specific data.

One wrinkle here is that roads that are at or near capacity may well have higher carbon emissions per vehicle mile than roads that aren't - more stop and start driving, more wasteful braking (unless you're driving a hybrid carefully). But against that, lower overall speed helps carbon emissions.

I suspect that traffic doesn't start discouraging driving until you are well into the higher emissions per car levels of traffic, unless the alternatives are already attractive compared to driving. Right at the margins, you might find that slightly increasing road throughput lowers emissions slightly overall, even as it discourages large changes to much lower emission transport.

There are smarter ways to increase throughput on the roads than just widening them though - well enforced variable speed limits, for example, which also lower traffic speed and thus emissions. And obviously it'd be stupid to do that without doing anything for real change to transport.

[shpalman]

widening of roads has "heartbreaking" downsides

[sTeamTraen]

One problem here is that non-smart motorways are also stupidly dangerous.

Less dangerous than normal roads.

In the UK you also have a lot of major trunk A-roads with the same 70mph speed limit as motorways, no hard shoulder, bicycles and milk floats allowed (IIRC - maybe only sometimes?), and vehicles joining from stop signs coming out of little side at 90 degrees.