An ineffective policy on city speed limits (From York Press)

Please answer this:

What is the average speed on a car journey through built up areas across York?

I would be very surprised if it were more than 20mph.

So why are you so concerned about a 20mph speed limit?

The 30mph limit in built up areas should be replaced with a 20mph one.

Less accidents and less injury with far fewr deaths.

Also you forget to mention that in Portsmouth the overall serious injuries fell by 22% after the 20mph schemes were introduced.

An increase in deaths could not have anything to do with people driving at 20mph but others speeding or travelling at 30mph plus.

The average speed is formed by smoothing out variations above and below. So whilst the average speed might only be 20mph, if you limit the maximum speed to that, you'll force the average down. Quite simple, really.

lis0r wrote:
The average speed is formed by smoothing out variations above and below. So whilst the average speed might only be 20mph, if you limit the maximum speed to that, you'll force the average down. Quite simple, really.

Totally wrong.

The average speed is how long overall it takes to get through traffic and congestion.

Because no one can travel at 30mph all the time in traffic in town the average will not be over 20mph.

If the limit were 20mph this would still apply as no one can travel on average faster than this.

Yeah, see, that's your fantasy, rather than reality, since I regularly manage to travel at 30MPH through the city centre with reasonable reliability, and even more frequently so on the roads outside the walls.

YorkToff wrote:

lis0r wrote: The average speed is formed by smoothing out variations above and below. So whilst the average speed might only be 20mph, if you limit the maximum speed to that, you'll force the average down. Quite simple, really.

Totally wrong. The average speed is how long overall it takes to get through traffic and congestion. Because no one can travel at 30mph all the time in traffic in town the average will not be over 20mph. If the limit were 20mph this would still apply as no one can travel on average faster than this.

Not sure who you’re asking – but when I travel across York (within the outer ring-road), and this would not be in peak times, my average speed is 18 mph. If I ensure that I never driver above 20 mph then my average comes down to 14 mph.

lis0r wrote:
Yeah, see, that's your fantasy, rather than reality, since I regularly manage to travel at 30MPH through the city centre with reasonable reliability, and even more frequently so on the roads outside the walls.

You can't travel at 30mph AVERAGE speed across the city centre it is not possible.

We are talking about average speed across a built up congested area not your fantasy of 30mph at all times.

far2bizzy wrote:

YorkToff wrote:

lis0r wrote: The average speed is formed by smoothing out variations above and below. So whilst the average speed might only be 20mph, if you limit the maximum speed to that, you'll force the average down. Quite simple, really.

Totally wrong. The average speed is how long overall it takes to get through traffic and congestion. Because no one can travel at 30mph all the time in traffic in town the average will not be over 20mph. If the limit were 20mph this would still apply as no one can travel on average faster than this.

Not sure who you’re asking – but when I travel across York (within the outer ring-road), and this would not be in peak times, my average speed is 18 mph. If I ensure that I never driver above 20 mph then my average comes down to 14 mph.

Ah but what you overlook is that if ALL vehicles travelled at 20mph or slower your average speed would be the same as at 30mph as all traffic would move more smoothly and uniformly.

Traffic tends to pile up so spurting at 30mph would just mean that queues of traffic form more often and become longer with more breaking and waste of fuel.

In any case 20mph is a decent limit in built up areas as you yourself admit your average speed is only 18mph with a limit of 30mph applied - and of course you may travel faster than 30mph at times you naughty, naughty thing you.

But th emain point is that being hit by a one ton scrap of metal is less injurious at 20mph than 30mph.

Nigel, no-one is talking about forcing a shift away from the car. The aim is to have fewer residents occupying hospital beds and mortuary slabs.

YorkToff wrote:

far2bizzy wrote:

YorkToff wrote:

lis0r wrote: The average speed is formed by smoothing out variations above and below. So whilst the average speed might only be 20mph, if you limit the maximum speed to that, you'll force the average down. Quite simple, really.

Totally wrong. The average speed is how long overall it takes to get through traffic and congestion. Because no one can travel at 30mph all the time in traffic in town the average will not be over 20mph. If the limit were 20mph this would still apply as no one can travel on average faster than this.

Not sure who you’re asking – but when I travel across York (within the outer ring-road), and this would not be in peak times, my average speed is 18 mph. If I ensure that I never driver above 20 mph then my average comes down to 14 mph.

Ah but what you overlook is that if ALL vehicles travelled at 20mph or slower your average speed would be the same as at 30mph as all traffic would move more smoothly and uniformly. Traffic tends to pile up so spurting at 30mph would just mean that queues of traffic form more often and become longer with more breaking and waste of fuel. In any case 20mph is a decent limit in built up areas as you yourself admit your average speed is only 18mph with a limit of 30mph applied - and of course you may travel faster than 30mph at times you naughty, naughty thing you. But th emain point is that being hit by a one ton scrap of metal is less injurious at 20mph than 30mph.

I agree with everything you say.

As you’re first 2 paragraphs say, it may very well be the case that if peak speeds are reduced, then the traffic may travel more smoothly (as indeed is proved by the introduction of 50mph limits around road-works on motorways) and so average speeds may remain similar.

But even if this is not the case the difference between 18 and 14 mph makes a difference of about 4 mins on a 5 mile cross-town journey – hardly the end of the world I would have thought.

Another factor regarding average speeds - Councillor Ayre says “ There is little evidence that a blanket approach causes a shift away from the car.” – I find it very hard to believe that, in York, if maximum speeds were brought down, there would not be some shift to cycling which in turn would reduce vehicle numbers and so increase average speeds for those who have to drive.

Another point I would make (I’m on a roll now) is that if maximum speeds were reduced then there would be a genuine opportunity for a rationalisation of traffic lights and panda crossings in the city and if that happens then average speeds would increase even further.

I can feel a slogan coming on – “Kill your speed – get there quicker”

far2bizzy wrote:
Another point I would make (I’m on a roll now) is that if maximum speeds were reduced then there would be a genuine opportunity for a rationalisation of traffic lights and panda crossings in the city and if that happens then average speeds would increase even further.

I can feel a slogan coming on – “Kill your speed – get there quicker”

You got there before me.

Yes we could remove almost all road signs and traffic lights and many panda crossings with proper road management.

You could say that motorists would work with pedestrians and cyclists.

However what I would love to see is a town gear built-in and marked as such into cars that prohibits the car to go more than 20mph.

Why not get a cyclist to ride in front of every car??

YorkToff - I see you in a new light, agree with every word!

sheps lad wrote:
Why not get a cyclist to ride in front of every car??

I usually overtake shedloads of cars in the City centre, especially at peak travel times.

pedalling paul wrote:
Nigel, no-one is talking about forcing a shift away from the car. The aim is to have fewer residents occupying hospital beds and mortuary slabs.

"The evidence used to support blanket 20mph limits is mixed. In Portsmouth, the UK’s first city-wide scheme, the number of people killed or seriously injured went up after the limit was lowered." DISCUSS

Torycouncil2015 wrote:

pedalling paul wrote: Nigel, no-one is talking about forcing a shift away from the car. The aim is to have fewer residents occupying hospital beds and mortuary slabs.

"The evidence used to support blanket 20mph limits is mixed. In Portsmouth, the UK’s first city-wide scheme, the number of people killed or seriously injured went up after the limit was lowered." DISCUSS

Well it’s a wet miserable day and I’m stuck indoors so I thought I’d have a look at the Portsmouth stats you are referring to – from the “Interim Evaluation of the Implementation of 20 mph Speed Limits in Portsmouth”
.

Yes the number of ‘KSI’ accidents went up from an average of 18.3 to 19.9 (an increase of 8%). The total accident figures, however, dropped from 163.7 to 129.4 (a decrease of 21%).

To quote the document - “Because the total numbers of deaths and serious injuries and of casualties by road user type and cause are relatively low, few inferences about the scheme’s impacts should be drawn from these figures.”

I actually agree with the letter writer, even though I cycle most places. 20mph in a modern city area is a stupid idea... Yes, in queues in the central part of the city the average speed is about 10mph, but you don't need 20mph along Haxby Road, Huntington Road, Hull Road etc... and also, on a bike when I know a car is behind me I'd rather it just overtake at a sensible speed with a good passing gap, rather than sit behind me because I'm doing about 17mph and they're sticking to the 20mph limit.

Even AndyD wrote:
YorkToff - I see you in a new light, agree with every word!

And (having read the other thread) I don't mean that in an 'obnoxious' way! Okay? :-)

YorkToff wrote:

lis0r wrote:
Yeah, see, that's your fantasy, rather than reality, since I regularly manage to travel at 30MPH through the city centre with reasonable reliability, and even more frequently so on the roads outside the walls.

You can't travel at 30mph AVERAGE speed across the city centre it is not possible.

We are talking about average speed across a built up congested area not your fantasy of 30mph at all times.

Wow, you are in *desperate* need of a remedial mathematics lesson.

Let's say Bobby travels across York - 1 mile at 30mph, 3 miles at 15mph. The average speed for that journey will ((1*30)+(3*15))/4=18
.75mph.

Now drop the speed limit to 20mph. The average speed for the same journey then becomes ((1*20)+(3*15))/4=16
.25mph. The average speed has dropped.

You're quite right, I can't travel at an average of 30mph without breaking the limit. However, you can't just drop the maximum speed limit yet leave average speeds untouched. It's basic babytown statistics that even a child could comprehend.

lis0r wrote:

YorkToff wrote:

lis0r wrote:
Yeah, see, that's your fantasy, rather than reality, since I regularly manage to travel at 30MPH through the city centre with reasonable reliability, and even more frequently so on the roads outside the walls.

You can't travel at 30mph AVERAGE speed across the city centre it is not possible.

We are talking about average speed across a built up congested area not your fantasy of 30mph at all times.

Wow, you are in *desperate* need of a remedial mathematics lesson.

Let's say Bobby travels across York - 1 mile at 30mph, 3 miles at 15mph. The average speed for that journey will ((1*30)+(3*15))/4=18

.75mph.

Now drop the speed limit to 20mph. The average speed for the same journey then becomes ((1*20)+(3*15))/4=16

.25mph. The average speed has dropped.

You're quite right, I can't travel at an average of 30mph without breaking the limit. However, you can't just drop the maximum speed limit yet leave average speeds untouched. It's basic babytown statistics that even a child could comprehend.

Wow you are patronising aren't you.

And you are making the basic error of applying basic maths to a complex chaotic problem.

In the real world things happen, obstacles, traffic queues, pelican crossings, traffic lights, differing traffic load, roadworks.

So your basic maths assumption does not add up.

And of course if traffic is limited to 20mph there would be less bottle necks causing better flow of AVERAGE traffic over distance hence my belief that the average speed would be perhaps faster than if the limit were 30mph.

Also your basic assumption of 1 mile at 30mph etc. is a fantasy when based on averages over time.

If the limit were lowered to 20mph we may even be able to get rid of many traffic lghts etc. to increase traffic flow even more.

But my basic mathematic premise remains undamaged, that lowering the speed limit in urban areas reduces fatal accidents and injuries overall, over time - yer know, the AVERAGE.