Smart motorways are (not) more dangerous

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nekomatic
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Re: Smart motorways are (not) more dangerous

Post by nekomatic » Fri Jan 31, 2020 12:07 pm

Martin Y wrote:
Thu Jan 30, 2020 1:06 pm
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?

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Martin Y
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Re: Smart motorways are (not) more dangerous

Post by Martin Y » Fri Jan 31, 2020 12:33 pm

nekomatic wrote:
Fri Jan 31, 2020 12:07 pm
Martin Y wrote:
Thu Jan 30, 2020 1:06 pm
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.

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Sciolus
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Re: Smart motorways are (not) more dangerous

Post by Sciolus » Fri Jan 31, 2020 7:58 pm

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.

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Martin Y
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Re: Smart motorways are (not) more dangerous

Post by Martin Y » Fri Jan 31, 2020 8:42 pm

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.

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