Re: Speed limiters

On 7/9/2024 9:26 AM, Martin Brown wrote:

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)

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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.

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I don't understand -- they are taking capacity OUT of service?

 No. In normal conditions it is standard motorway 70mph limit and 3 running lanes one hard shoulder. When it gets busy the speed limit drops to 60 (then 50) and the hard shoulder becomes a running lane.

Ah.  Here, the road would be widened (construction project) if traffic
suggested that need.  Road widening often plans ahead for even more
lanes not deemed necessary at the present time.
In town, this is a traumatic event as the additional width comes at
the expense of the homes/businesses located along it.  So, a 6 lane
(common through town) roadway grows to 8 by appropriating frontage
from the businesses located along its length.

In that latter mode a cross in a lane indicates an obstruction in that live lane so you have better slow down and/or get out of it.

Here, a police officer (assuming it is a "recent accident") dispatched to
the scene will take measures to redirect traffic around that lane(s).
This can be done with silly orange "dunce cones", parking their patrol
car in the lane with "lights" active, standing and manually redirecting
traffic, etc.
Last week, a 4 ft dia tree toppled onto a 6 lane roadway.  Police cars
were deployed to block traffic that would encounter those lanes until
a crew could get the tree off the roadway (the stump is still located
where it pulled out of the ground as there is less concern over its removal
as it doesn't impact traffic)

Emergency vehicles have to fight their way through traffic if something happens (as opposed to going down the non-running lane hard shoulder).

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That seems to be a bigger problem "in town", here.  Largely because
traffic is naturally stopped at frequent intervals along any travel
route.  Convincing three lanes of "parked" (at traffic signal)
traffic to get the hell out of the way for an emergency vehicle
approaching from behind is a bit of a chore.

 UK drivers are mostly quite good about opening a path for emergency vehicles. What they don't do well is zip merging.

It is difficult to locate the direction of the vehicle's siren
(there have been numerous studies to determine what sort of
"noise" would best assist observers from making this determination).
Here, it's largely a surprise as to where the vehicle will appear.
The strobe mentioned below is acknowledged by the intersection
mounted sensor with a similar ~1Hz strobe.  Observant drivers
noticing that flashing will treat it as forewarning of an approaching
emergency vehicle.  Noticing which traffic direction gets enabled
is a further hint as to where the vehicle is located (i.e., if
YOU are given a signal to progress, then the vehicle is either
behind you or approaching you from ahead; if you are held stopped,
then the vehicle is approaching from left or right)

Such vehicles are equipped with a strobe light that visually signals
a sensor mounted high in the intersection.  It ties in to the local
signal controls and overrides the timing to allow traffic along
the "approach axis" to move, even if it would normally be halted.

 Nothing like that here or if there is then it is cryptographic. Where I live the PM (previous) moves about quite a lot and it is done by 16x police motorcycle outriders going ahead and escort vehicles followed by a bunch of heavies.
 

In theory, that traffic starts moving (making the blockage more
fluid) and they can then get out of the way of the approaching (from
front or rear) emergency vehicle.
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Too often, drivers "freeze" thinking that the emergency vehicle can
sort out its dilemma.  For undivided roadways, the emergency vehicle
will often cross the centerline to use the lanes in the opposite
direction to get around idiot drivers "ahead" of it.

 The drivers freezing is silly places problem is common in the UK too.

I suspect part of it is the requirement that one "pull over to allow
the emergency vehicle to pass" (how can I pull over when there is someone
stopped to my right?) along with not knowing where to expect the
vehicle.
A few weeks back, I was approaching an intersection, saw the strobe
at the sensor, knew the vehicle was traveling along my "axis" (because
I had a green light) and was able to notice it (a fire truck) in my
rear view mirror.
The intersection was packed with stopped vehicles in all lanes, "frozen".
I pulled into a left turn cutout and stopped *immediately* -- leaving
multiple car lengths of that lane clear all the way to the intersection.
The driver of the fire truck cut in front of my "parked" position and
I could almost *feel* his gratitude as he would otherwise have been
blocked from passing (divided roadway so he's stuck on this side!)
[It is policy, here, for a fire truck to be dispatched with each ambulance
so it is most likely NOT a fire that is being addressed but some person
in distress]

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

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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.

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Our "interstate" highways tend to have a large median between divided
lanes.  So, crossing over the "center line" ends up with a vehicle
in grass/ditch.

 We don't have enough real estate for that. Motorways where the opposing lanes are more than 10' apart can be counted on the fingers of one hand.

Even "in town", it is common to find an extra lane of grassy "median"
between lanes going in different directions.  These are frequently
planted with foliage to help cut down the glare of oncoming headlights.
For points where significant numbers of traffic might need to turn
left prior to a normal intersection, a "left turn lane" is carved
out of this median to allow cars to queue "to the left" (left being
our fastest travel lane) without impeding vehicles behind.

Police officers are often at risk in roadside stops as the *vehicle*
may be on the shoulder but the officer standing beside the driver's
door/window will have his ass out in traffic.
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["distracted drivers" care little about what they may hit!]

 UK the advice is to get out of the car and stay behind the crash barrier. Cars on the hard shoulder get hit with monotonous regularity.

If pulled over by a police officer, you are prohibited from leaving the
vehicle -- for the officer's safety.  Keep your hands in plain sight, etc.
If suffering a breakdown, you pull over (soft shoulder or breakdown lane)
and exit the vehicle when safe to do so.  Or, hope a patrolman will
come along and protect your vehicle (with his own).
People carry flares, flashing warning lights, etc. to deploy on the roadway
to enhance their chance of being seen by drivers coming up behind them.
I tell SWMBO to simply call me and sit still until I arrive if she ever
has a problem.  Just manhandling the wheels (for a flat) would be beyond her
abilities!
Other people "subscribe" to roadside assistance services who will handle
the problem (when they can)

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

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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.

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Police will usually walk back upstream and deploy flares to warn of their
stationary presence, "ahead".

 Similar but no flares. HGV's will protect a serious crash site though I've only been in one major incident as the first car to stop without hitting anything and was then protected by the HGV behind me.

There is no such requirement (or tradition), here.  Truck drivers are just
as eager to get through/past a slowdown/stoppage as anyone else.  They will
share that sort of information with their peers ahead/behind as a courtesy
for others to plan their routes to meet their delivery schedules and driving
constraints (a commercial driver can only operate a vehicle for a fixed
time before a rest is required, by law; you don't want to waste three of
those driving hours sitting in a freeway parking lot!)

It was reported as 3 HGVs and a car. But it was actually a single car that clipped the central reservation 2 or 3 times and then swept across the live lanes totalling a couple of cars as it went. The HGV driver behind me had a QD dashcam with higher viewpoint which was used in evidence.
 It is reckoned that for every hour of stationary traffic queue on a UK motorway there will be one serious rear end shunt (in addition to the original incident that caused the queue). Sometimes rubberneckers on the other carriageway cause a separate incident.

No idea if there is a similar statistic, here.  Distractions from operating
phones while driving are common.  The son of the guy who installed our HVAC
(many years ago) was in court defending himself from killing a woman and her
infant who were walking along the road while he was trying to tune his car
radio.
It is illegal to "operate" a phone while moving (hands free interface required;
though I question how much better that is).  If you are wise, you will set your
phone on the seat beside you (or in the center console) as a passing police
officer can ticket you if he sees it in your hand while the vehicle is in motion.