30kmh – making streets liveable

[jezer]

When driving I take great satisfaction in keeping strictly to the speed limits, or less if appropriate. I just watch the other drivers queuing up behind, anxious to break the law. If a driver behind is on the phone I slow right down, well I've got to protect other road users from a moron who is not paying attention to his surroundings

[Mark1978]

Doing 50mph on the motorway is even more ... interesting. But I get great MPG!

[Rob Archer]

I've heard it said (by police officers and other road safety campaigners - links to conclusive evidence would be useful!) that most 'habitual' or 'careless' speeders break the limits by a proportion. E.g. someone who regularly drives at 36 mph in a 30 limit (20%) will drive at 24 mph in a 20 limit. The result is, that whilst many drivers's aren't sticking strictly to the limit, the average speed is brought down, with all the benefits of safety, lower emissions etc. Of course, getting everyone to drive at 20 or less would be desirable, the key objective has been achieved.

There is obviously still a problem with deliberate, reckless speeders - that's where the enforcement comes in.

[kwackers]

I've heard it said (by police officers and other road safety campaigners - links to conclusive evidence would be useful!) that most 'habitual' or 'careless' speeders break the limits by a proportion. E.g. someone who regularly drives at 36 mph in a 30 limit (20%) will drive at 24 mph in a 20 limit. The result is, that whilst many drivers's aren't sticking strictly to the limit, the average speed is brought down, with all the benefits of safety, lower emissions etc. Of course, getting everyone to drive at 20 or less would be desirable, the key objective has been achieved.

There is obviously still a problem with deliberate, reckless speeders - that's where the enforcement comes in.

In the past when I was bothered looking all the surveys showed that in the absence of any physical restrictions a 20mph speed limit has very little impact on speed. (Something like 1mph reduction in average speeds). However combine it with physical traffic calming and you get much greater reduction, but then you I suspect that leaving it at 30mph and adding the traffic calming would have the same effect.

I was walking through Harrogate earlier along a 20mph road and I'd have estimated almost everyone was doing 35-40mph with one woman in a BM easily doing in excess of 50 (with kids in the back).
I'm all for 20mph limits but they need both policing and a change in attitudes from drivers.

[patricktaylor]

... 20mph limits but they need both policing and a change in attitudes from drivers.

That's true, as long as speed limits are seen (by some drivers) as part of a game to be played against the police rather than part of civil society. At speed traps they still flash warnings to drivers coming the other way, as if we are all in it together, playing a beat-the-cops game. I don't think the change in attitude thing will come easily, and not for many years. Physical traffic calming seems essential in the meantime.

[thirdcrank]

IMO a problem with the traffic calming around here is that it may slow down traffic but it does so at the expense of distracting drivers and often making them anything but calm. An annoyed driver isn't necessarily a safer one and if traffic calming involves a competition for space or a race for priority, cyclists will generally tend to come off worse.

I presume there are other ways of of achieving calm traffic but if there are, they have bypassed this part of the world.

[patricktaylor]

Those chicane contraptions are certainly infuriating - they are just cheap 'add ons'. I think speed bumps work better but doing it properly (calming) means altering the look of the street so it doesn't seem so much like a scaled down highway but a different kind of space with law enforcement as a last resort. It costs money though.

[xerxes]

the average speed is brought down, with all the benefits of safety, lower emissions etc.

As I said in my previous post, the problem with a 20mph limit is that it leads to higher, not lower, emissions.

[kwackers]

the average speed is brought down, with all the benefits of safety, lower emissions etc.

As I said in my previous post, the problem with a 20mph limit is that it leads to higher, not lower, emissions.

And 50mph is more efficient still.

There's an argument that if you make the roads safer for vulnerable road users fewer of them will feel the need to armour themselves up in 2 plus tonnes of steel and be more prepared to walk and use bicycles.
There's also the issue that a lot of the time doing 30mph (plus) simply means you'll join the end of the queue faster and end up sitting in traffic burning fuel yet going nowhere.

With such things in mind, fuel consumption is actually difficult to quantify and varies based on location. There's little doubt though that the roads are much more pleasant with slower traffic than with fast traffic and in the event of a collision there's no doubt at all that slower speeds reduce injury.

[thirdcrank]

Yes.

Casualties, emissions and car parking are some of the disadvantages of combining motor traffic with residential streets. If the starting point is that everything else is secondary to the needs of motor traffic, the result is where we are now.

[Mark1978]

IMO a problem with the traffic calming around here is that it may slow down traffic but it does so at the expense of distracting drivers and often making them anything but calm.

And makes life horrible for cyclists too. There's a street near me that has chicanes, and they are always a big stress to go through on my bike as cars are trying to nip through ahead of me, even if I take primary. There's a cycle bypass one way but it's always full of debris, so I have to move out to the right, which again is risky. It would be better for all concerned if they were just removed.

[squeaker]

As I said in my previous post, the problem with a 20mph limit is that it leads to higher, not lower, emissions.

I'd be interested in seeing some evidence for that, as the only serious study I've read (EU funded, I think) concluded that the overall effect on gaseous emissions was broadly neutral.

[Mark1978]

As I said in my previous post, the problem with a 20mph limit is that it leads to higher, not lower, emissions.

I'd be interested in seeing some evidence for that, as the only serious study I've read (EU funded, I think) concluded that the overall effect on gaseous emissions was broadly neutral.

Don't know if it's by design or just how cars are but I know most cars I've driven aren't happy in any gear at about 20mph.

[kwackers]

Don't know if it's by design or just how cars are but I know most cars I've driven aren't happy in any gear at about 20mph.

Every car I've ever driven has been perfectly "happy" at 20mph (in as much as cars can be happy...)
I suspect it's a psychological thing in that it's the driver rather than the car that isn't "happy" and probably has a lot to do with peoples lack of experience in driving at anything below 35...

[squeaker]

Don't know if it's by design or just how cars are but I know most cars I've driven aren't happy in any gear at about 20mph.

Partly a result of the ridiculously high power to weight ratio of many modern cars and the desire for 'performance feel' (ie small accelerator pedal movement gives large change in throttle opening), I suspect. The old (IAM? or just the economy driving exponents?) trick of having a small block adjacent to the accelerator pedal so you can roll you foot sideways to minimise jerky movements would help, as would wearing light shoes.