Safe Speed Forums

In another topic Dixie found the new Welsh figures...



They contain a bit more data than we have had before on 20mph zones.

- 20mph zones have higher injury crash density than 30mph zones
- 20mph zones have higher average crash severity than 30mph zones

There are quite a few possible explanations for these counter-intuitive results:

- maintaining 20mph takes too much attention
- they have placed 20mph zones in the most dangerous places
- a greater proportion of crashes involve pedestrians, who are less well protected
- 20mph zones create a false illusion of safety, making them more dangerous

We have long known that 20mph zones have higher average crash severities. This is the first time we have also discovered that crash density is higher.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

It is cause or effect?

Is there any data showing the current and previous crash density/severity in a 20mph zone where the limit was previously 30mph?

There are two 20 zones I negotiate on my daily route in to work. In all cases they start and end with an exhaust-threatening speed cushion and at least one supplementary speed cushion (but more gentle) in the middle. One of the middle speed humps coincides with a place where pedestrians cross to and from a small parade of shops.

I am certain that low-speed collision risk has been increassed compared to as it was prior to the interference, resulting from the combination of the following, in no particular order:

* general low speed causing complacency of both motorists and pedestrians.

* braking by approachging motorists for the speed hump being wrongly read as a "come across" by pedestrians.

* motorists' eyes fixed for too long on the close-by tarmac to time braking and lift-off to minimise car damage at the expense of hazard scanning.

* eyes to the speedo too often and for too long

* some cars approaching the speed cushion impact point at unusual angles to give separate front wheel contacts (a quarter of the damage by each blow compared to a full axle assault at a given speed) taking pedestrians' and other motorists' attention (who then can collide with one another, while the driver causing the distraction is not involved further).

* cars keeping very close to the gutter to allow one set of wheels to circumvent the speed cushions that stop short of the kerb, slowing at the same time, combined with pedestrians anticipating the car not slowing down so much and stepping under the back wheel with toes.

I'm sure I read somewhere that speedhumps should not continue to the kerb at equal height, such that they may be misconstrued as a raised zebra crossing, causing a right of way conflict between motorists and pedestrians.

I can typically avoid the bumps with one set of wheels, but there are some that go all the way across.

You need to go to Rushden...they've got some there 4 inches high and edged with concrete....one cost me a catalytic converter...

I bloody hate speed bumps. If everyone stuck to the speed limit we wouldnt need them would we?

I don't suppose we do need them - the roads haven't got safer since they 'took off'.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

The only places we "need" them are places where any sensible driver wouldn't be approaching 30mph. The drivers who would won't be slowed down by speed bumps, many will take even more irresponsible action to keep up their speed.

I think that dpends on whether or not you're a Chav. I saw an interesting episode not so long ago at the junction to a main road to the street where I live. Near the junction is a speed bump. On one side of the road a Chav family had gathered. Chav dad and Chav junior step out into the road on top of the speed bump. There's a Merc coming up the street. Instead of crossing the road, they both put out their hands singnalling the Merc to stop so that Chav mum and sprog in pushchair can cross the road.

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Anyone who tells you that nothing is impossible has never bathed in a saucer of water.

ALL of the humps on our estate go kerb to kerb, and the drains which are built into the kerb stone to allow water to pass the hump blocked in yar one, and have NEVER been cleared.
Consequently there is a pool behind every hump, and at the edges, the camber of the road means this can be deep.

We also have a hump with chicane on a bend - meaning traffic approaching at 20 mph cannot see oncoming traffic until less than 20 feet from the hump!

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

I'm actually coming round to these a bit

I can remember on one of my very early posts here saying that I thought all bumps, chicanes etc should be banned & that cameras should be retricted to schools etc.

One of the things I found since joining safespeed is that I think an awful lot more about safety issues whilst out driving & I realised a few weeks ago that I've changed my views on this.

I just don't believe that cameras work from a safety perspective & thus it seems pointless putting them round schools. But we'd all agree that kids particulary at primary schools are unpredictable, so I concluded that bumps would be the best solution in those areas.

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Wake me up when the revolution starts
STOP the Toll Tax http://www.traveltax.org.uk

why not tech kids road safety instead?

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Welcome to the UK, the Land of "Selective Freedoms"

As well, not instead.

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Wake me up when the revolution starts
STOP the Toll Tax http://www.traveltax.org.uk

This speed hump outside schools topic has been discussed before but my view is that if you are focussing on the hump so as to ensure crossing it without damaging your car then you are NOT focussing on the kids at the side of the road.

My view is that flashing speed signs before the school zone advising of the low speed limit focusses the driver on the road ahead due to the preception there must be a hazard ahead.

I own a car that is set at the minimum road legal height and I scrape the bottom of my car on about 50% of speed humps so my hate for them bounds on a passion.

On many of them I have to actually brake on the down side of the hump at 1mph or less. I have to do this to ensure the suspension does not compress as the front wheels reach the bottom of the hump in order to avoid the bottom of the car hammering the top of the hump.

People following get really annoyed when they are driving any standard car and so their attention is on me rather than pedestrians as well.

ALL humps that have a centre point that is above the legal minimum clearance of a car according to the law should be removed or shaved to an appropraite height!

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Ross

Yes I'm a hoon, but only on the track!!!!

But in those areas, at the times children are around you don't need traffic calming because even the most determined boy racer can't manage over 10mph due to all the semi-abandoned 4x4s.

Far from discouraging the school run, we should encourage more cars to clutter up the roads outside schools. That way you have natural, time dependant traffic calming.

Fife council at the moment are steamrollering their way through making every 30mph limit in the county a 20mph limit with speed bumps. The amount of the things is quite incredible,and I too hate them with a passion. The senseless implementation of 20mph limits absolutely everywhere drives me totally insane though, and has taken away any benefit these zones could have in areas outside schools etc. One area in particular that is to be bumped and a 20 next year is nowhere near any houses or schools, but is being brought down purely because of the presence of a single bus stop.

SURELY there should be some kind of legislation to prevent councils reducing limits to utterly unrealistic levels across a whole county? I have tried objecting, but of course they just sidestep you and blunder their way on with it anyway.


From their own site....

"The programme to install more 20mph zones continues, and eventually it is intended that the majority of roads in residential areas, except distributor roads, will have 20mph speed limits."

This is the problem with everything these days. If it seems like a good idea, it gets misused to such an extent that it becomes commonplace and is no longer a good idea.

I wonder if this effect happened with cameras? The first few, people pay attention to, then they become common & therefore ignored?

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Wake me up when the revolution starts
STOP the Toll Tax http://www.traveltax.org.uk

I think it's safe to say that the bumps modify driver behaviour in a variety of diverse, unpredictable and often incompatible ways.

Personally I speed up for most speed bumps as I have found that the optimal speed for minimising back pain is around 33mph. Lower or higher and it hurts more.

We also have:

- People driving down the middle of the road to try and squeeze into the gap between bumps
- People who try to hit them dead centre (often bringing them within a few inches of parked cars, so even less time to spot the muppet crossing from between them
- People who put their left wheel into someone's driveway, then drive with their left wheel on the grass verge and their right wheel in the gap between cpeed bump and curb, then use the next driveway to get onto the road again.
- A small number of nutters (I have only ever witnessed one) who will just put their entire car on the grass verge and stay there for the entire length of the road.
- Speed bumps that aren't even pointing in the direction of travel, usually catching people out at the last moment and causing a sudden direction change in order to maintain their preferred method of hitting a bump.
- Speed plateaus constructed from brick or tile that like to become solid sheets of ice in the winter. (One of these got me as a pedestrian somewhere in Cambridgeshire even after having identified the danger whilst in the car and negotiated it accordingly)



So in otherwords, we really need figures for 20 zones that have remained otherwise unmolested vs 20 zones that are filled with speed bumps vs these same roads when they were 30 zones.