[alancalverd]

Not sure I follow. The Highways Agency "logic" is to retrofit concrete barriers on roads with significant rapid traffic, regardless of accident rates. In doing so they need to close a lane and restrict the speed of traffic in other lanes. My question is, quite simply, if it ain't busted, why fix it, if fixing it means causing congestion and possibly (usually) increasing the accident rate in the constricted area. Listen to Radio 2 any rush hour to see how much fun they cause!

The other stroke of genius has been to "widen" motorways by turning the hard shoulder into a running lane and instituting a "smart" motorway system. Once again, the works involve closing the left-hand lane and squeezing the traffic into one or two lanes with a 50 mph limit  for months at a time (the new carriageway isn't just a layer of asphalt on the hard shoulder - it all has to be dug out and built to full carriageway standard, plus a whole load of monitoring and warning equipment). When the job is done we have the intriguing spectacle of HGVs running at 60 mph on the new track until they hit some poor bugger who has stopped with a problem because there is nowhere else to go. Not just me but the AA and RAC have pointed out that "smart" motorways are dumb.

The best barrier solution I have seen was to plant wild roses and brambles in the central reservation.  Unlike wires, which ping the wandering vehicle back into the traffic lane, or concrete  blocks which destroy it, thorn bushes are an excellent energy absorber,  a great habitat for small wildlife, and don't reflect or destroy the vehicle. Maintenance is a doddle: run a hedge trimmer along the lane a couple of times a year, and the barrier gets stronger.

[Bored chemist]

if it ain't busted, why fix it,

People die in accidents, so the mechanisms for the prevention of accidents are busted.


Removing the hard shoulder is, as you say, dim. But it's not a lot to do with your original point.

In this weather, thorn bushes are combustible but...

un a hedge trimmer along the lane a couple of times a year,

and watch the thorns puncture tires while the very same energy absorbing brushwood you created is now on the road.

[alancalverd]

People die in accidents, so the mechanisms for the prevention of accidents are busted.

Agreed, but whilst speed cameras are installed on the basis of accident statistics, modifying central reservation barriers appears to be done on the basis of safety statistics: an average of 25,000 vehicles passing a point every day implies that the road is safe!

Rose and bramble thorns don't puncture car tyres, and I'd hope that the contractors would sweep up after them, as they do on minor roads (the dangerous ones!). Interesting statistic: the strategic road network (motorways and major A roads) accounts for only 2.4% of UK road space but carries 33% of the traffic.

Back to electrical transmission losses, anyone?

[wolfekeeper]

Not sure I follow. The Highways Agency "logic" is to retrofit concrete barriers on roads with significant rapid traffic, regardless of accident rates. In doing so they need to close a lane and restrict the speed of traffic in other lanes. My question is, quite simply, if it ain't busted, why fix it, if fixing it means causing congestion and possibly (usually) increasing the accident rate in the constricted area.

Accidents that happen when everyone is going in the same direction can be bad, but they are as nothing to what happens when a car leaves a carriageway and ends up going into traffic travelling the other way. The concrete dividers are designed to bounce the cars back into their own lane, and generally have better outcomes.

Without a concrete divider, if a car does end up entering the opposite lane, if the traffic rate is low, then the chances of a nasty accident is much lower anyway. So you only replace them on the high flow rate roads where the relatively expensive equipment does the most good.

[vhfpmr]

The other stroke of genius has been to "widen" motorways by turning the hard shoulder into a running lane and instituting a "smart" motorway system. Once again, the works involve closing the left-hand lane and squeezing the traffic into one or two lanes with a 50 mph limit  for months at a time (the new carriageway isn't just a layer of asphalt on the hard shoulder - it all has to be dug out and built to full carriageway standard, plus a whole load of monitoring and warning equipment). When the job is done we have the intriguing spectacle of HGVs running at 60 mph on the new track until they hit some poor bugger who has stopped with a problem because there is nowhere else to go. Not just me but the AA and RAC have pointed out that "smart" motorways are dumb.

Smart motorways are safer:
https://www.bbc.co.uk/sounds/play/p09kxjnc
(From 8 mins)

[vhfpmr]

The best barrier solution I have seen was to plant wild roses and brambles in the central reservation.  Unlike wires, which ping the wandering vehicle back into the traffic lane, or concrete  blocks which destroy it, thorn bushes are an excellent energy absorber,  a great habitat for small wildlife, and don't reflect or destroy the vehicle. Maintenance is a doddle: run a hedge trimmer along the lane a couple of times a year, and the barrier gets stronger.

There's a hedge here. It did absolutely nothing to stop a lorry embedding itself in that thatched cottage.
https://goo.gl/maps/hSqRSahXgfGvximx7

[SammyS7]

Depends on distance, quality of transmission devices, how much of transmission system is high voltage vs. lower outlet voltage like 120 volt. Line loss can be much higher but it really depends on the specific power system involved be it High voltage or low and quality of the system, connections, transformers etc. Remember, there is power loss even if no one is using the power as transmission, source, connections, even weather and temperature all have an effect on power transmission and loss.