Mayor of London Consultation - cleaner air

[Sally Eva]

Do you have a theory why 20mph is a difficult speed to maintain but 30mph is easy?

[DulwichLondoner]

If the limit is 30mph, like I said, I can easily keep the speed between 25-29 without constantly looking at the speedometer (and away from the road).

If the limit is 20, I either constantly look at the speedometer, or must keep a speed of around 15, which is ridiculously low, causes even more congestion, gets the other motorists insanely angry at me, etc etc.

Next time you drive in town with a passenger, ask him/her to check the speedometer and tell you how often you go above the 20mph limit.

The reason most of the civilised world allows a minimum tolerance is precisely because it would be stupid, dangerous and counterproductive to get motorists to spend more time looking at their speedometer than at the road.

[rendelharris]

We won't revisit our discussions about the efficacy of 20mph limits DL, as we (ironically) argued each other to a standstill! Though I will point out that when you say "RoSPA, for example, don't recommend setting 20mph limits throughout 100% of a council" - they say they don't recommend 20mph for trunk roads with no significant residential buildup, shopping areas, schools or high pedestrian footfall. Not that many roads of that description in ED.

But I still can't get this argument about it being difficult to drive at 20mph. Surely anyone who can't cope with sticking to any set speed on the road is somewhat lacking in the necessary skills to pilot a vehicle safely? When I rode a motorcycle I didn't find it difficult to stay at 20mph when required, and I certainly wouldn't make any claims to having been a particularly skillful rider. In modern vehicles with digital speedometers I really can't see an excuse beyond incompetence for being unable safely to adhere to the posted limit.

[bels123]

uncleglen Wrote:

-------------------------------------------------------

> Nigello Wrote:

> --------------------------------------------------

> -----

> > I hope you asked the driver to switch off.

> No I didn't because the last time I asked a van

> driver to switch off I was threatened.....

Totally get using caution when asking people to stop idling. I?m doing it almost daily but am selective and generally only when I?ve got the kids to make the argument stronger.

If you don?t feel comfortable asking, Southwark enforce against idling now, ?80 fine - call ‭020 7708 8587‬ and they should send a traffic warden

[DulwichLondoner]

The point about keeping below the 20mph is not that it's difficult to drive at a constant speed (it's not), but that in city traffic you practically never do. You're constantly slowing down and accelerating and slowing down etc etc. Which means you are constantly looking away from the road and at the speedometer because by going just 1mph above you can be fined a % of your weekly earnings.

I have no intention to revisit the whole discussion, either. We have different views about the need to have robust evidence before implenting expensive changes that cause lots of disruption. You support cycle lanes and 20mph speed limits despite the lack of clear evidence in favour of both!

I'll just remind you that in both cases I never said I know they are wrong, I said the advantages have not been proven, which is different.

As for RoSPA:

"RoSPA does not believe that 20mph?

speed limits are suitable for every road in a local authority area. They should be targeted at roads that are?

primarily residential in nature and on town or city streets where pedestrian and cyclist movements are high (or?

potentially high), such as around schools, shops, markets, playgrounds and other areas. Roads which are not?

suitable for 20mph limits are major through routes. "?

[DulwichLondoner]

bels123 Wrote:

> - call

> ‭020 7708 8587‬ and they should send a

> traffic warden

The same ones that clumsily ride 125 scooters with flip up helmets not homologated to be used in the up position while riding? I'd love to have them fined... 😀

[rendelharris]

DulwichLondoner Wrote:

-------------------------------------------------------

> As for RoSPA:

>

> "RoSPA does not believe that 20mph?

> speed limits are suitable for every road in a

> local authority area. They should be targeted at

> roads that are?

> primarily residential in nature and on town or

> city streets where pedestrian and cyclist

> movements are high (or?

> potentially high), such as around schools, shops,

> markets, playgrounds and other areas. Roads which

> are not?

> suitable for 20mph limits are major through

> routes. "?

Which is exactly what I said, and somewhat different to your disingenuous presentation of it previously. What roads around here don't their criteria apply to? Sections of the South Circular, maybe - which aren't 20mph anyway.

Oh, and if you're going to quote RoSPA: "A large number of evaluation studies have demonstrated a link between the introduction of 20mph zones and a subsequent reduction in casualties. The size of the reductions and the consistency of results over a wide number of areas are further evidence for this link.

There is similarly strong evidence showing the benefits of traffic calming measures, which are used in 20mph zones."

[micromacromonkey]

There was a top gear episode where the presenters stopped being dicks for a few minutes and attempted to accelerate to 30mph and hold that speed without looking at the speedo. They did pretty well, and I suspect the reason for it is that we are conditioned to drive at that speed through experience. So 20mph is only more difficult because we aren't so used to it.

[DulwichLondoner]

If you read between the lines, RoSPA?s own fact sheet

https://www.rospa.com/rospaweb/docs/advice-services/road-safety/drivers/20-mph-zone-factsheet.pdf [Nov-2017]

presents cases where 20mph limits are associated to safer roads, and cases, e.g. Portsmotuth, where the evidence is simply inconclusive.

Bath is another example where, again, the evidence was inconclusive.

What beggars belief is that none of these studies starts by analysing what the main causes of injuries are, and what can be done about them. Changing speed limits has no impact whatsoever on injuries caused by driving under the influence, driving at crazy speeds, or road users acting like idiots (pedestrians crossing against the red man, cyclists undertaking trucks turning left, motorists doing u-turns where they shouldn?t, etc.).

For example, a big risk factor is the presence of cars parked on the street, because they hide those idiotic pedestrians who jump in the middle of the road without looking. I?d guess a 30mph road where you cannot park is safer than a 20mph road with cars parked!

In reality, I suspect the impact on traffic during rush hour is not huge, but can be massive at night when roads are emptier; journey take longer, so vehicles are on the road for longer, polluting more and for longer.

Also, unless it?s digital, when you look at the speedometer, can you really tell whether you?re doing 20 or 21mph? I struggle, but I appreciate that all forum users are incredibly better car drivers and motorcycle riders than myself, so my case doesn?t count?

If you haven?t switched off and are interested in the details:

In Portsmouth, casualties reduced but KSIs [killed and seriously injured] increased; however, and this has always been one of my points, ?the relatively low numbers of recorded KSI casualties in Portsmouth mean that small fluctuations up and down by chance can have an undue influence on this?; in other words, if you go from 2 to 3 accidents it?s technically a 50% increase, but practically the numbers were too low to begin with to be able to meaningfully infer anything.

Bath witnessed a similar increase in KSIs. The Councillor?s admission in this interview is very telling:

-----

https://www.telegraph.co.uk/news/2017/12/17/20mph-limit-dangerous-costly-reverse-council-admits/

"It has cost over ?800,000 to roll out the 20mph zone and it would probably cost the same to reverse them.

"We just haven't got the money. I'm pretty sure the 20mph zones will stay in place for the foreseeable future."

It adds that the rise in casualty numbers and severity would "suggest against further expansion of area based schemes."

----------

This biologist didn?t agree, and laudably went through the trouble of digging up the original report, criticising its lack of statistical rigour (I agree ? but the same reservations apply to the studies that support 20mph limits!) and running some statistical analyses. His conclusion? That ?there is no significant effect of introducing 20mph zones on the number of people KSI.? No. Significant. Effect. Neither positive nor negative!!!

https://medium.com/@lewisspurgin/20mph-zones-are-not-causing-more-deaths-37d41e30e297

[DulwichLondoner]

rendelharris Wrote:

What roads around here don't their

> criteria apply to? Sections of the South

> Circular, maybe - which aren't 20mph anyway.

We have already had this conversation. In my opinion, most red routes: most of the A3 stretch from Battersea Rise to Elephant and Castle, Camberwell new rd, the A202 from Camberwell green to New Cross Gate, etc. In your opinion, only some stretches of the south circular.

I am very familiar with the part of the A3 around Oval and Kennington : perfect example of mostly straight road, with excellent visibility, limited number of pedestrians (no real high street, schools, etc.). In roads like this, riding my motorcycle at 20mph can actually be dangerous, as car drivers get angry and aggressive and often attempt dangerous overtaking.

micromacromonkey Wrote:

-------------------------------------------------------

> There was a top gear episode where the presenters

> stopped being dicks for a few minutes and

> attempted to accelerate to 30mph and hold that

> speed without looking at the speedo.

Interesting. But I'm assuming they weren't driving in congested London roads, right?

[rendelharris]

DulwichLondoner Wrote:

-------------------------------------------------------

> I am very familiar with the part of the A3 around

> Oval and Kennington : perfect example of mostly

> straight road, with excellent visibility, limited

> number of pedestrians (no real high street,

> schools, etc.). In roads like this, riding my

> motorcycle at 20mph can actually be dangerous, as

> car drivers get angry and aggressive and often

> attempt dangerous overtaking.

Well I'm not surprised - because the speed limit there is 30mph.

[Penguin68]

I think you may find that UK cars are tuned so as to be optimised running at 30mph (on the flat) in 4th gear. You could re-tune them to optimise around 20mph, but that wouldn't make sense where most built-up areas (outside Southwark) still have a 30mph limit. At 20mph you either have to run in 3rd, or accept slightly rough running in 4th. Clearly running in 3rd all the time in built-up areas is not very economical on fuel use. The car 'wants' to (is tuned to) run quicker than 20mph, hence the problems some people feel at maintaining that speed. For an experienced driver the car doesn't 'sound' or feel right at 20mph, so they unconsciously drift up. I suspect that's also why the experienced Top Gear drivers found it easy to drive at a constant 30mph, as the car felt right (was tuned to feel right) at that speed.

[DulwichLondoner]

Kennington road, A23, is 20mph: https://goo.gl/maps/9zdRY3zHdu62 despite being wide, straight, and with very few pedestrians (again, no high street, no schools, etc).

The A3 between Brixton and Elephant and Castle, well, I simply assumed it was 20mph because the councils have implemented 20mph limits throughout, and there are no 30mph signs (I have just reviewed the whole Oval from Kennington stretch on street view). My bad, then, but possibly TFL (which controls red routes) could have put a 30mph sign because it?s not ******* clear at all

[rendelharris]

DulwichLondoner Wrote:

-------------------------------------------------------

> The A3 between Brixton and Elephant and Castle,

> well, I simply assumed it was 20mph because the

> councils have implemented 20mph limits throughout,

> and there are no 30mph signs (I have just reviewed

> the whole Oval from Kennington stretch on street

> view). My bad, then, but possibly TFL (which

> controls red routes) could have put a 30mph sign

> because it?s not ******* clear at all

I haven't seen any signs on the road (but then you don't usually get signs on 30mph roads, do you?) - I guess it's deducible from the fact that there are no 20mph signs (which I believe are compulsory?). When you pull on to the A3 from any side street there are signs saying you're leaving the 20mph zone and entering a 30.

Long stretches of the A23 (Kennington Road) are actually not much wider, if at all, than a standard residential street in terms of the space available when the bus lanes are in operation - 20mph seems perfectly reasonable along there. I agree there are sections of it that would be suitable for 30mph, but then you'd be changing speed limits every couple of hundred yards which would obviously lead to confusion and accusations that it was all a trap.

[DulwichLondoner]

rendelharris Wrote:

> When you pull on to the A3 from any

> side street there are signs saying you're leaving

> the 20mph zone and entering a 30.

Not from all. I guess this must have contributed to my confusion.

Eg there are here: https://goo.gl/maps/JmSVQboELx12

but not here: https://goo.gl/maps/yEss1bU3jBu

Anyway, my bad - I was wrong on that road being 20mph, not much to debate there.

[rendelharris]

DulwichLondoner Wrote:

-------------------------------------------------------

> rendelharris Wrote:

> > When you pull on to the A3 from any

> > side street there are signs saying you're

> leaving

> > the 20mph zone and entering a 30.

>

> Not from all. I guess this must have contributed

> to my confusion.

> Eg there are here:

> https://goo.gl/maps/JmSVQboELx12

> but not here: https://goo.gl/maps/yEss1bU3jBu

>

> Anyway, my bad - I was wrong on that road being

> 20mph, not much to debate there.

To be really, really nerdy - that photo without a warning is in 2015 - Lambeth (where Kennings Way is) didn't go 20mph boroughwide until 2016, so there probably is a sign there now! I'll get me coat.