Re: Speed limiters

On 07/07/2024 18:51, Don Y wrote:

On 7/7/2024 2:56 AM, Martin Brown wrote:

Investment in "smart motorways" which allows them to use all 4 lanes as live running lanes (3 properly designed to be running lanes and one hard shoulder intended as a refuge for broken down vehicles).

 How does "smart" make that possible but "not-smart" doesn't?
Do your roadways "change directions" based on time of day?
(we have center lanes that do so to expedite traffic into
or out of busy areas based on traffic patterns -- but, they
are time driven)

In theory the smart motorways are monitored along their length by cameras and control rooms. Each lane has a tick or a red cross above it to indicate if it is in use or not available. At peak times all lanes are run live which leaves no room for error whatsoever.
Emergency vehicles have to fight their way through traffic if something happens (as opposed to going down the non-running lane hard shoulder).

 [IIRC, DC? had similar roads that would change direction
based on time of day]

There were a few of those in the UK. One in Manchester London Road 4 lanes under flow control depending on the time of day. 3 in for morning rush hour and 3 out in the evening they were notorious for head on crashes. Picture from the late 1970's:
https://www.flickr.com/photos/gmts/33623521145
An even worse configuration in the 1970's was the three lane trunk road with the centre lane for "overtaking only". They resulted in the most spectacular head on crashes (think 150+mph closing speeds) and caused collateral damage in the adjacent lanes. Not survivable.

 Most roads have predefined lanes in each direction.  Some roadways
are further (physically) "divided" to isolate traffic from each
direction.

UK motorways have strict central reservation barriers which are being reinforced to heavy weight solid cast concrete with tensile steel inside to stop the larger HGVs going straight through them.

 

It didn't take account of dumb drivers or of the need to properly maintain the camera systems used to monitor the road situation. As a result they are having to add a lot of extra refuges to the "smart" motorways to make them safer after several very high profile nasty high speed collisions between motorway traffic and broken down vehicles.

 Stopping *on* the roadway is often forbidden.  Your vehicle must be
pulled off, onto a shoulder (outside the outside lane -- far right in
our case).

That is the point of "smart" motorways. There is no hard shoulder to pull off onto - it is a live lane just like all the others. You can't always control where you breakdown either. There are refuges from time to time but far too far apart to be any use.
In my student days we got stuck immediately behind a vehicle in the outside lane (long before mobile phones). What happened next was very interesting. A pair of heavies saw what had happened from a distance behind us and created a rolling road block. When they had stopped all the traffic we got out and pushed the dead car onto the hard shoulder and then got back in our car and continued our journey. It was touch and go whether someone would pile into us when we had to stop like that.

A patrolman encountering such a vehicle will likely park his vehicle
upstream of it to further alert oncoming traffic to the hazard.

Same in the UK. Highways agency vehicles have damn big flashing please don't hit me signs with an arrow that can be erected behind them.

Work on the roadways (overhead signage, pavement, etc.) usually results in
overly long stretches being cordoned off ("dunce cones") to ensure traffic
is clear of the work area BEFORE encountering it.

There is a lot more of that work at the moment because of the crisis with smart/dumb motorways. They are dumb as hell when the smarts that are supposed to keep them safe are not working!

 And, most roadways enter and exit on the outside (right) lane so you
can predict where the "varying" traffic will originate.

Opposite sense in the UK, but we do have a few free for all junctions on urban motorways where traffic is injected and must leave from the outside (fastest) lane. A recipe for high speed collisions.

 

The smart motorways I drive regularly I have such totally misleading and misguided signs that I no longer trust them to tell the truth. Worst example I saw was alternate gantries showing 40mph speed limit(as low as it actually goes on a motorway) and 60mph. I think the control room were messing about to see what traffic chaos they could cause.

 The closest thing to "smart" here is signage that may dynamically
reflect some condition of interest (amber/silver alert, construction
ahead, etc.).  We have some automated technology that warns of haboobs
in areas prone to them as they instantiate in time frames too short to
erect manual signage (radar).  I'd wager there are parts of the midwest
where similar systems warn of tornados.

They could be a useful if they were properly maintained and drivers understood them. Unfortunately neither condition is met in the UK.
There are also variable speed limit motorways and roads equipped with the latest average speed camera technology. That is also part of smart.
--
Martin Brown