Discussion in 'Motoring' started by mjn, Mar 12, 2017.
Petition: Raise the Speed limit on Motorways in the UK from 70mph to 90mph.
I'm behind it in theory. When the speed limit was made 70 mph most cars were barely capable of 100mph and had poor brakes and handling compared to modern cars.
However for the speed limit to be raised there would need to be a massive push towards raising driver skills. Roads are getting busier and driving standards are getting lower. Test scores etc may not show this but what I see out and about is generally quite shocking.
And shocks me as well , a lot of cars are pushing over 80 mph now with a 70 limit , raise it to 80 and they are going to think 90 is safe , plus you will always have slower traffic like HGV , faster cars , less reaction time , recipe for disaster , because as above , driving standards are generally shocking nowadays ....
Generally I'd like to say yes but when you spend enough time on the motorway you realise too many people shouldn't be driving on it in the first place. We don't deserver a higher limit.
10 Years ago I'd have said yes but in recent years drivers seem incompetent.
The limit should be raised BUT the driving test should be 2 part. It's crazy that you can drive on the motorway unsupervised with no previous experience.
Is a 3 lane motorway any different to a 3 lane A road ? ....
No hard shoulder for starters, and there aren't many 3 lane A roads. Plus, one of the lanes usually filters off after a short while.
Obviously, i'm only using the roads near me as an example.
A more sensible move would be to remove the 56mph limit on HGVs. Traffic would flow a lot more smoothly without cars travelling at 60mph having to pull out to overtake them.
Not sure i would want 44 tons doing 80mph !!!
No, it would be better to keep HGVs to lane 1 of 2 lane motorways during peak times, like they do abroad.
To back up your local observations, the A23 near me, at the bottom end of the M23, is mostly three-lane for the 20 miles to Brighton.
There is a hig difference in the nature of the A23 and the M23. The M23 has fewer bends, nothing like as many on-off slip roads, not to mention those hard shoulders.
The design of junctions is also different.
Is there a petition we can sign to reduce the speed limit to 55 mph?
I loved it when driving in the USA and that was the post-energy-crisis speed limit.
Then again, Americans don't all see themselves as F1 drivers who have to compete with everyone else on the road. Perhaps it is down to all those automatic transmissions.
The same is true of the M1 near where I live. Unlike other "smart" conversions, here the shoulder is now permanently another lane.
I'd be in favour of higher limits when the motorways are quiet. Since stretches of motorways such as the M1 and M62 have variable limits to lower the limit when there's lots of traffic why not increase the limit above 70 when it's safe to?
They are already banned from the outside lane 24/7 in the UK?
It's down to the space they have. It never feels like a battle in the US because there is generally plenty of space on the roads.
Yes, but if you have the joy of using a 2 lane motorway like the northern end of the M11 the queues built up while trucks overtake one another without breaking the speed limit are really frustrating.
You sometimes have the ridiculous situation of 30-40 cars following 2 trucks, one was going fractionally faster downhill but as they take so long to pass as they start to climb the next hill it stops making ground and slips back. The whole motorway is then stuck down to 55mph or whatever the truck in lane 2 can manage up a hill.
I appreciate that trucks are working but it does make your blood pressure rise after miles and miles.
e.g. Google Maps
No. Too many idiots on the motorway as it is.
I work in highway maintenance (specifically highway structures on motorways), so looking at this from an alternative perspective - a 'simple' change of speed limit, would be cost prohibitive. Every linear metre of vehicle restraint system on the motorway network would require replacement / upgrading.
The reason for this is that while a barrier can withstand an impact of above 70mph, it's approval for use is based upon a limit of 70mph. Were that to be upped, every barrier system in use would require assessment, and the older ones - in particular bridge parapets, would need replacement.
It gets more complicated still because a parapet is only as strong as the edge beam it's anchored into. If you stiffen up the parapet, the concrete beneath needs to be able to take it otherwise the entire edge beam will just pop off. The result is deck strengthening and parapet upstand replacement works to bring it up to standard.
Since those seeking an 90mph limit tend to have less than polite things to say about road works already, it would be interesting to know how they'd feel to have every motorway underbridge in the country having significant upgrade works in order for their motoring-nirvana aspirations. I'm not sure who would pay for it - while VED is being ring fenced for infrastructure from 2018, that will barely be enough to cover the planned refurb works already in the pipeline, let alone replacing steel and concrete VRS up and down the land.
On the topic of road works, an increase in speed limit would also require a lengthening of lead-ins for traffic management (you cannot step traffic down to a 40-50mph limit with a 30mph step).
It's a nice idea, but when the above is factored into the equation, along with the points mentioned above about enough people running out of talent at 70mph, it's a recipe for a very expensive disaster.
IMO the motorway speed limit should be reduced to 60 mph. Also cars should be designed to travel no faster than 80 mph.
I don't quite understand this - surely speed is only one factor - mass is another that has just as big if not a bigger impact (no pun intended) on this.
My understanding of Physics isn't at PhD level, but...
So why is it that heavier lorries have been allowed on the road since 1969 , but faster cars aren't?
Speed and mass make up the kinetic energy in a moving vehicle.
If a collision occurs the kinetic energy determines the severity of the crash in the form of a transfer or exchange of energy.
The exchange of energy = (half of vehicle mass) x (speed of vehicle squared).
This means a small increase in speed leads to a big increase in the severity of the collision.
There's not a simple answer for this - but regarding vehicle weights (lorries in this instance). The 60mph speed limit for HGV's is the design criteria used for vehicle restraint systems (coaches that can travel quicker than this are also tested - 70mph in their case, not exceeding 12m in length). The use of concrete step barriers in central reserves was a move in the right direction as it helped reduce crossovers i.e. a vehicle going through the central res and ending up on the opposing carriageway - these have tended to be HGV's suffering blowouts / being blown around in gales etc.
In recent years (mid 2000's on) H4A systems were brought in. These are high containment vehicle restraint systems that protect railway bridges and overbridge piers and supports that fail impact assessment loading i.e. a HGV would muller a regular steel beam barrier, clout the pier and cause enough damage to make a deck failure a possibility.
The knee jerk reaction to this is probably someone saying "why not use high containment barriers everywhere". Again this is cost prohibitive, but more critically, there isn't the physical space on the network - barriers are designed with several criteria, two of those that are never spoken about, being set back and working width. Your set back is the horizontal distance from front of barrier beam to either front of kerb or traffic side of rib line. The higher the speed, the greater this distance is (it allows errant vehicles more room to correct their trajectory on their way to a collision).
Working width is the distance from the front of barrier beam (or base of concrete barrier) to its displacement point after it's been hit i.e. how much does it get shunted in a collision. Again, the higher the speed, the more displacement. You cannot have an obstacle like a bridge pier in the working width the barrier itself will clout the pier rather than the vehicle.
You're absolutely right regarding mass having an influence as well as speed. The crux of the issue is that the UK motorway network was built around a 70mph speed limit. To up this is more a simple moving of the goal posts. It's highly unlikely there'll be the spending available in our lifetime to rebuild the motorway network to allow for a higher speed limit.
Of course, this doesn't stop people speeding - but barriers are type approved and signed off to restrain vehicles at their designed speeds, not above that. Many drivers have had accidents at speeds above 70mph without 'incident' so to speak, but that's more down to the factor of safety in the barrier / structure design, rather than it being inherently capable of withstanding such collisions frequently.
The thing to take into account along with everything mentioned regarding barriers, is that the almost everything on the motorway would have to change. The following are items that you see every day on the motorway and wouldn't think twice about, but would need to be altered if an increase in speed limit was brought in:
- Lane lines: Rib lines would possibly need to be wider, lane separator lines longer and gaps bigger.
- Road studs (cats eyes) would then need to be moved or replaced to tie in with the fore mentioned lane lines.
-Road signs: Junction signs, distance signs, you name it - they're all sized so that at 70mph they can be read. At 90mph they would be too small therefore would end up being remade larger - in many locations there isn't room between the carriageway edge and the highway boundary (fence / ditch) to install a larger sign, and we aren't in a position to buy more land (this is a point relating to smart motorways, another topic that isn't explained to the public in enough detail - but I'm not going into that one ).
I am finding that disturbingly interesting.
On the 55mph stuck behind lorries frustration; I e found a bizarre change in my attitude since getting an EV. I want to maximise the range rather than minimise the time taken. Doing 65, 60 or even 55 behind a lorry feels normal and way less frustrating now.
Stepping back a little to look at what this is actually supposed to achieve. I'm guessing it's a quicker smoother flow of traffic which therefore reduces journey times?
A quick look at some of our European neighbours can help here. Better driver education would be a great start. Driving on the left unless overtaking really does free up space in the middle and outside lanes. There has been a push recently aimed at 'middle lane hoggers' but it's still a major bottleneck on a fast otherwise free flowing artery. Likewise LGV'S overtaking each other at almost identical speeds. This has a huge effect on faster traffic compared to the small gain achieved by the individual LGV. I personally would like to see LGV's overtaking banned from two lane carriage ways and restricted from areas around major intersections. The French protect the inside lane near exits and on ramps with a solid line to reduce last minute sudden lane changes. It works well.
And a personal favourite of mine - I would like to see the speed limit for LGV's increased to 65.
So, reduce the bottlenecks in the system and the end result will be a smother faster journey. And let's be honest, the 'real' speed limit for cars on motorways is already higher than 70.
All this talk of how we'd need larger writing on signs, better bridge supports, etc
How do our French cousins cope with an 80mph limit and of course our German cousins with no limit in some sections? I don't recall seeing any larger fonts on signs, but i do see a better standard of lane discipline. They also don't have longer slip roads, but instead have a 130kph limit around junctions.
The French and German highways aren't designed and built to the DMRB (Design Manual for Roads and Bridges). Different countries do things differently, they have their own standards - in this country we have to adhere to our standards. The DMRB is based on a 70mph motorway limit, hence the items I mentioned above being affected by a speed limit change.
My understanding exactly.
So why has the potential kinetic energy in lorries been allowed to increase enormously since the introduction of the motorway speed limit, but not the potential kinetic energy of cars?
Surely the bigger factor is the "weight" of the lorry going from 12 tons to whatever it is now, 38? tons.
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