Justin Smith wrote: ↑Tue Jun 22, 2021 07:26
JRN wrote: ↑Mon Jun 21, 2021 22:32
Justin Smith wrote: ↑Mon Jun 21, 2021 21:26
I have never been comfortable with the idea of "Smart motorways" but we need extra capacity for as little money and land as possible so I reckon I could cope with Smart motorways
provided they are like the original M42 was. That was significantly different in that originally the hard shoulder was BY DEFAULT a
non running lane and
only became a running lane when traffic was in danger of grinding to a halt. Critically when the hard shoulder became a running lane there was a blanket 50mph speed restriction enforced with speed cameras. I believe that is a compromise that people could live with.
Some people may think 50mph is too slow, but I do not, it's paradise compared with being stood still or in a walking pace traffic queue.
I liked the original M42 implementation, but subsequent Dynamic HSR schemes were worse than ALR to be honest.
Most of the ALR schemes are pretty similar and consistent. The M4 scheme is a little different construction-wise due to extensive bridge replacement, but will deliver a similar driver experience.
Contrarywise, each DHSR scheme is pretty much unique, and I think this contributed to the perception that they were confusing.
The M42 scheme used the HS as an additional running lane for extra capacity between junctions; each junction was a lane drop to D3M, the hard-shoulder turned into the slip-road for the next junction. It wasn't that confusing.
But subsequent schemes tried various ways (there was more than 1 implementation) of providing "through-junction" running, and I think that's where it became too much for the average motorist.
Also the M62 scheme was a rather odd mish-mash of DHSR, ALR, and Managed Motorway on an existing (widened) D4M.
Is my memory right ? The original M42 was NOT permanent all lane running ? The hard shoulders were by default NON running lanes and, critically (from a safety point of view) ONLY became running lanes with a 50mph limit ?
Sorry for any confusion. Your memory is correct. The original M42 was not, and still is not, permanent All Lane Running (ALR). It was (and is) Dynamic Hard Shoulder Running (DHSR).
What I meant by my post about how the M42 scheme was implemented was that that is how it works
when the scheme was in operation.
As in, when the Hard Shoulders are open, they are open between junctions, and then there is a sign that says hard shoulder ends, and then the hard shoulder effectively turns into the sliproad for the next junction. It's a neat way of adding a little extra capacity between junctions.
The M42 is not the only DHSR scheme. A few schemes on the M6 in the Birmingham area also used DHSR, and outside the West Midlands so did the:
M4/M5 scheme by Almondsbury (Bristol)
M62 scheme around Leeds (Mixture of DHSR, ALR, and Managed Motorway on a widened motorway with Hard Shoulders)
M1 Jct 10-13
However many of these schemes chose to use rather more complicated variants of DHSR, including ways of allowing extra capacity
through junctions, which increases the complexity, and potential for driver confusion.
In general I think ALR is superior to these schemes.
All the DHSR sections of Motorway are set to be converted to ALR by 2025.
Also I believe the Max speed allowed for when the hard shoulder is open on DHSR schemes is 60 mph.