Is it better to concentrate traffic flows on one route, or multiple ones?

[JonathanH]

From https://www.railforums.co.uk/thread...should-happen-now.255534/page-24#post-6471269

Likewise I wish another motorway had existed West of London rather than tinkering (widening) with the M25. Its all down to Nimbys and environmentalists (not saying thats bad but it costs).

Where would this other motorway west of London go? How would it be accessed from the east?

On a more general point, is it better to concentrate traffic on one route or have multiple routes?

(I appreciate that the M25 is the amalgamation of a number of different Ringways around London but that plan was removed many years ago, and there are obvious physical issues which prevent different routes.)

 

[Bletchleyite]

On a more general point, is it better to concentrate traffic on one route or have multiple routes?

With roads, without a doubt multiple routes, as very often a crash will close one entirely, and so multiple routes is more resilient.

Milton Keynes is the ultimate - if you close a grid road it has barely any effect as the traffic just redistributes onto the others.

 

[JonathanH]

Milton Keynes is the ultimate - if you close a grid road it has barely any effect.

Yes, on a local basis I can very much see that, but there is a limit to whether that sort of grid can exist on a wider basis.

 

[Bletchleyite]

Yes, on a local basis I can very much see that, but there is a limit to whether that sort of grid can exist on a wider basis.

It probably can't, but as one example having the M6 Toll is vastly preferable to doubling the width of the existing M6 (were that practical - we know it isn't of course). Thus bypasses add resilience as well as capacity.

The M6 around Lancaster is a notable pain in this regard - if it's closed due to an accident, there are no decent diversionary routes, and so the entire of Lancaster ends up gridlocked. It would almost be better rather than any widening of that to add another route for more local traffic, e.g. a bypass and extra bridge up the west side of Lancaster connecting J33 and the Bay Gateway. (I'm well aware there are nature related reasons that's unlikely).

 

[ABB125]

Multiple route, no question. Most other countries seem to grasp this, but in the UK we seem to prefer putting all our travel eggs into one basket. Which often ends up just as expensive as the better option, just worse

 

[stuu]

The M6 around Lancaster is a notable pain in this regard - if it's closed due to an accident, there are no decent diversionary routes, and so the entire of Lancaster ends up gridlocked. It would almost be better rather than any widening of that to add another route for more local traffic, e.g. a bypass and extra bridge up the west side of Lancaster connecting J33 and the Bay Gateway. (I'm well aware there are nature related reasons that's unlikely).

All of the M6 north of Wolverhampton surely, at least as far as Lancaster. A Lichfield-Bolton motorway would add a lot of resilience and capacity to the road network

 

[BayPaul]

From https://www.railforums.co.uk/thread...should-happen-now.255534/page-24#post-6471269


Where would this other motorway west of London go? How would it be accessed from the east?

On a more general point, is it better to concentrate traffic on one route or have multiple routes?

(I appreciate that the M25 is the amalgamation of a number of different Ringways around London but that plan was removed many years ago, and there are obvious physical issues which prevent different routes.)

https://pathetic.org.uk/unbuilt/m31/

Joining the A3 to reading, connecting to the M4 at the A329(M) junction. It would have allowed all M4 and M3 - M25 South traffic to avoid the busiest part of the M25. Quite a clever plan.

 

[Peter Sarf]

From https://www.railforums.co.uk/thread...should-happen-now.255534/page-24#post-6471269


Where would this other motorway west of London go? How would it be accessed from the east?

On a more general point, is it better to concentrate traffic on one route or have multiple routes?

(I appreciate that the M25 is the amalgamation of a number of different Ringways around London but that plan was removed many years ago, and there are obvious physical issues which prevent different routes.)

I was thinking roughly
M3 North East until hitting the M25 route somewhere near the M1
M40 South East until hitting the M25 route somewhere near the A3
Those two would cross each other somewhere on the West side.
Obviously they would not be straight routes because London is in the way.

Alternative is M40 High Wycombe anticlockwise to the M3 extended either way at a later date to the A3 and M1.

https://pathetic.org.uk/unbuilt/m31/

Joining the A3 to reading, connecting to the M4 at the A329(M) junction. It would have allowed all M4 and M3 - M25 South traffic to avoid the busiest part of the M25. Quite a clever plan.

That would improve on the route I drive. From Croydon to Stroud, Bristol and now Cardiff I have for decades, from Croydon left the M25 and gone down the M3 one junction then worked my way round to the A329(M) and then onto the M4 West. I hate going past Heathrow and that is a longer way round so normally slower. A more motorway grade route would help there.

I also nowadays set off East from Croydon to the A3 at the Tolworth tower so as to miss another part of the M25 and the extra benefit is that the A23 Croydon to the M25 is uncannily slow. More recently I totally avoid the M25 by turning SW off the A3 just before the M25 and head for the same junction I used to turn off the M3 at then continue towards Reading.

Big downer is all that does not lead to the M40. Except I am now considering, once leaving the A329(M), turning onto the M4 back towards London and then going up the A404 to High Wycombe. A two hour journey to Banbury is often 3 hours midday and coming back can be even worse even on a Sunday.

 

[david1212]

Overall multiple routes. Concentrating traffic on routes generally means that for a proportion the ( theoretical ) fastest route is significantly longer than one using even only mostly single carriageway 'A roads' rather than also 'B roads'. As already stated when there is disruption the alternative using major roads is often very long so traffic diverts onto the secondary roads which as well as towns and villages become slow if not gridlock.

An example of multiple routes is around Birmingham and Coventry with the M5, M6, M42, M40 and M45 plus A46. The problem is all run beyond design capacity for much of the day so become very slow if traffic from any one is rerouted. The M40 was only extended beyond Junction 8 because the M1 and M6 could not handle the traffic flow.

South from the M4 there is no reasonably fast and free flowing route between the A34 and the M5. Had a dual-carriageway road been built from say Swindon to Dorchester it would take some traffic off both the secondary roads and the major routes.

 

[Peter Sarf]

Another disadvantage of a single bigger route is that junctions and roads around have to cope with more traffic. I seem to recall that point being noticed when the M25 became six lanes past Heathrow. I often see queues on the Westbound M4 for the M25. Those queues can fan out backwards onto all four lanes of the M4 or even the three lanes past the Heathrow junction. Now the A3/M25 junction is being rebuilt to cope with the traffic the M25 produces.