Speed Bumps are not effective "traffic calming" but an ineffective "Band-Aid" for poorly designed streets. Examples of more effective ways to calm traffic

A few days ago I tweeted about how speed bumps are used in the UK as a band-aid on streets which should have no through traffic. This perhaps requires a little more explanation.

No-one likes speed bumps
Speed bumps are unpopular everywhere. There are claims that they delay emergency services, even that they can injure some people transported by ambulance. Speed bumps cause damage to cars and lead to drivers slowing down to cross the bump before accelerating, which increases exhaust emissions and noise pollution. What's more, speed bumps are very unpleasant to cycle over and can cause danger to cyclists.

Most speed bumps shouldn't exist
Sadly, speed bumps seem to have become synonymous with traffic calming in many peoples' eyes. The problem with installing speed bumps as traffic calming is that the "solution" doesn't match the problem. Rather than attacking the cause of traffic problems, especially on residential streets where problems are typically due to their being used by through traffic, traffic is allowed to continue while an attempt is made to regulate speed by means of speed bumps. This approach has very serious limitations.

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Assen barely uses speed bumps at all
The city where we now live provides many good examples of cycling infrastructure, road and residential street design. We operate cycling infrastructure study tours from this location in order to demonstrate these concepts. In comparison with a British city of a similar size, Assen has very few speed bumps. See the photos below for examples both of poor and good practice

Bad examples
First the bad examples. Standard disclaimer: These photos and a video demonstrate where "traffic calming" is ineffective. Don't copy anything from them. Click here to go straight to the good examples.

An example from the UK. In an attempt to reduce speeds, seven speed bumps have been installed in a street of less than 500 m. However the problem with this street is the through traffic and these speed bumps do not address that problem. Using this street allows motorists to avoid a longer journey with traffic lights and is a rat-run especially during rush hour.

Another example of bad practice in the UK. This street has six speed bumps in 500 m but again becomes a rat-run during rush hour because it accommodates through traffic. The problem is exacerbated by allowing bidirectional usage when the street is so narrow. I once had to push my daughter off her bike between parked cars along here because a driver heading towards us at excess speed clearly had no intention of slowing.

Speed bumps are sometimes combined with restrictions (horizontal traffic calming) such as that shown here. But these also do not address the problems caused by allowing through traffic. Note that this street in London has both a 20 mph speed limit and is posted as a through cycle-route. This doesn't mean that conditions are good for residents or for cyclists as you can see from the video below.

Residents of Gillespie Road in London are campaigning for better conditions, using video of the rat-running traffic in their street. No-one should have to live with behaviour like this on their doorstep. I wish them luck with their campaign.

Speed bumps are not only used in obvious residential streets in the UK, but also sometimes on through roads like this. The road looks like a race-track but the speed bump requires slowing to around 10 mph. This bump rather took me by surprise on my last visit to the UK when I drove here in the dark at the posted speed limit of 30 mph. This is again bad design. There is no reason why drivers are expected to slow sharply at this point. Locals will learn about this. Otherwise it is unpredictable.

Good examples

Now for some good examples, all of which are residential streets in Assen which don't have a traffic problem. Assen has almost no rat-running. In the case of newly built areas, opportunities to take short-cuts though residential streets were designed out. In the case of older areas they have been re-designed out. Streets are "calmed" by means of reducing traffic and by designing streets which do not encourage high speeds, not by causing motorists to have to abruptly slow for obstacles.

If you would like to copy this success, rather than risk losing the context of these examples "in translation", we suggest a study tour in which you can be shown how these examples and others work.

30 km/h residential street in a 1970s suburb. While this is at times a busy through route by bicycle, there is no through route here for motor vehicles so motor traffic is restricted to residents and visitors.

50 km/h road in a 1970s suburb. There is more traffic here than on the 30 km/h street, but the traffic here also is residents and visitors only. There are no through routes by motor vehicle anywhere in this suburb and therefore there is no through traffic. Note raised table for the pedestrian and cycle-crossing. 

1970s suburb, brand new asphalt. The surface is suitable for high speeds, but the road layout is not. This is a non-through route. A cul-de-sac with no traffic other than that of the neighbours. Children play safely on the street here.

On the left, an example of a street in a newly built suburb. The yellow street on the left has been designed to encourage low speeds both by choice of surface material and by eliminating straight lines. At the same time, the white cycle-bridge makes cycling more attractive by providing cyclists and pedestrians with more direct journeys than are possible by car.

Retro-fitted junction between residential streets in a 1950s suburban area. The entire junction is a raised table. Note bollards used to encourage drivers not to cut the corner.

The reason why streets in a 1950s suburb do not suffer from rat-running is that the majority of the streets have been made into an elaborate one-way system specifically to break up through routes. The intention was not to make cycling difficult and therefore cyclists are always excepted from the one-way system. All the one-way streets in Assen serve to reduce motor traffic and they are therefore not comparable with those in the UK and other countries.

Another example of a one-way street in an older residential area in Assen. The one-way system is used to eliminate through traffic, except by bicycle.

Smoothly raised "roundabout" junction between residential streets in an older area. This makes it obvious to drivers that they should not speed, while causing little if any problem for cyclists.

The Netherlands has the most extensive network of low speed streets in the world. Almost all residential streets in Assen (and across the Netherlands) have 30 km/h speed limits. However, it's important to note that the calm nature of these streets is due to the removal of traffic more than it is due to the speed limit. Merely posting a lower speed limit is not effective.

This residential street is close to the city centre and perhaps attractive to people trying to avoid parking fees. Parking bays are provided for residents. The car on the left is not legally parked. Read more about residential car parking in the Netherlands. This is one of Assen's rare speed bumps. It's smooth to cycle over through not ideal with three wheels.

As we get very close to the city centre, where drivers would find parking on residential streets to be desirable, parking is for residents only (zone 6). The blue sign with a red bar bans on-street parking from that side of the road. The allowed side of the road for parking alternates, and this emulates the planned meandering road as seen in the newer suburbs.

In 2009, this obvious through route in a residential area had an obvious speed bump with cycle-bypasses. In itself, this is reasonably well designed. However, it was not necessary because this street does not actually suffer from much through motor traffic. See the next photo.

By 2012 the bollards had been removed and the speed bump had been made smoother. In reality, while this is a main route for cyclists (it continues as a bicycle-path from the point ahead with the circular blue sign) there is very little motor traffic here. Through traffic is removed by the one-way streets elsewhere. Note that while this street is one of the rare places in Assen where cyclists "share" the street with buses there is no bus-stop bypass.

People often mistakenly believe that the tiled surfaces of Dutch roads are historical. Actually, they're often very modern. This photo shows a street being transformed from wide asphalt to narrower tiled surface with off-street car parking. Read more about residential car parking.

A street which was transformed slightly earlier than the example in the last photo. Note that this is part of a one-way system which excludes through traffic.

In an older residential area, one of the narrowest streets in Assen. This is again part of a one-way system which excludes through motor traffic. By excluding through motor traffic, conditions can be made good for walking and cycling even on the narrowest of streets. Note how parking is allowed on one side of the street only. This alternates, emulating the planned meandering road as seen in the newer suburbs.

We've demonstrated these ideas to study tour participants for many years. In this example I'm explaining about one-way streets in Assen on a study tour. On the next Study Tour (September) we will again demonstrate a variety of residential street treatments.

Not everything is perfect in the Netherlands
While the Netherlands leads the world in such things as calming of residential streets, that does not imply that everything here has equal value. The Netherlands is a work in progress and problems can be found here too. These two examples are of residential streets in Assen in which there are problems, though these problems are at a much lower level that those illustrated by the British examples above:

A plastic doll, Victor Veilig, is requesting that drivers using this street should slow down. That a resident felt the need to buy this doll and install him on the street is an indication that all is not well.

Planters used as horizontal traffic calming. This street is not massively attractive to through traffic because it parallels a much more suitable road. However, these planters would not have been installed unless they were believed to be necessary and that indicates not all is well with this street. 

Even the relatively smooth and well designed speed bumps in Assen cause problems for some users. Any bicycle with more than two wheels, such as this machine being used by a person with a disability person, can't fit around the side of the speed bump. That problem is magnified when there is also an illegally parked car.

Speedbumps on the cycle-path

Something often misunderstood about Dutch cycle-paths are the speed bumps. We don't have any to show you in Assen, but there are a few in Groningen. This is one of them, on my commuting route:

Children riding to school cross a device designed to reduce the speed of a slow class of moped which is permitted to use this cycle-path

What's important to keep in mind is that these things are not to slow down cyclists. Policy requires that cyclists' journeys are made more direct and faster. These are intended to slow mopeds, not bikes, and you find speed-bumps like this on main cycle routes where mopeds are also allowed.

These speed bumps are larger than might be obvious from photos (especially photos with no cyclists in them). I measured this one at 10 m long by 3.75 m (32' x 12 '). 3.75 m is of course also the width of this cycle-path. Note that pedestrians have their own separate path.

A drain built into the gutter prevents
flooding.

The distance between the humps or dips determines the speed at which you can ride over these.

At normal cycling speeds, you barely notice that you've ridden over a speed-bump like this. If you cycle faster, then you do need to be aware of them.

I've found that 35 km/h is on the edge of being uncomfortable over this speed-bump. That's quite typical. I guess at that sort of speed the speed-bump ought to warn me as well as the mopeds about the upcoming road junction (behind the camera).

Note also the lighting to preserve social safety at night-time. The upcoming tunnel, which gives cyclists a short-cut under the railway line, is always lit.

Another set of speed-bumps at the junction of two main cycle-paths in Groningen. You can see this speed bump in action, slowing mopeds, in a video here

Bromfietsen and death
It is quite often the case that people from outside the Netherlands, not to mention those born and bred here, greatly overestimate the danger posed by bromfietsen and snorfietsen - the small mopeds / scooters which are allowed on some cycle-paths.

There are two classes of mopeds. The slow ones can travel at up to 25 km/h, the same speed as an electrically assisted bicycle, and don't require the rider to wear a helmet. These are allowed on the cycle-paths in just the same way as are electric assisted bicycles. The faster mopeds are limited to 45 km/h and require the rider to wear a helmet. These are not allowed on urban cycle-paths but are allowed on some rural cycle-paths, where they occasionally provide entertainment for faster cyclists.

How many are there ?
It's also worth reflecting on how few mopeds there are. Due to being noisy and smelly and attracting attention as well as criticism, people often greatly overestimate the number of mopeds in the Netherlands. Actually their numbers are much smaller than people think.

1. At the main railway station in Groningen which currently has parking for more than 11000 bicycles, there is space provided for only about 10 mopeds.
2. In the most remote suburb of Assen, where for every 100 people there are 116 bicycle trips per day, just 3 trips per day are made by moped.
3. In a video which shows cyclists crossing a bridge, one moped makes more noise than several hundred bikes

Mopeds are about as common as bicycles are in the UK or USA. They are exposed to much the same bias against them, including claims that they are dangerous, as are bicycles in the UK or USA.

Who rides mopeds ?

Mopeds are largely ridden by elderly people who generally ride responsibly. In general mopeds are not considered to be particularly aspirational and they're not really very fashionable. This is reflected in their relatively low numbers. You'll rarely see mopeds parked outside a school which caters for higher educational standards so there's a degree of snobbery about who might be seen on a moped. In some areas they're ridden more often by immigrants so we also can't rule out a degree of casual racism.

Mopeds ridden by teenagers are, perhaps unsurprisingly, not always ridden responsibly. Teenagers also quite often make simple alterations to the machines which remove the speed restrictions (similar models are sold in other countries without the speed restriction devices fitted here). This is quite a good way to get pulled up by the police and the machines can be confiscated as a result.

In the Netherlands, moped riders are an out-group just as cyclists are elsewhere and they are subject to similar prejudice.

How lethal are they ?
How lethal are these mopeds ? Almost certainly less so than you think.

I've not been able to find any data to support the hypothesis that injuries due to badly ridden mopeds are a really major health issue in this country. As Toby Sterling put it, "scooter deaths (amazingly!) were a rounding error." as well as pointing out that you are "more than twice as likely to be murdered in Amsterdam than killed while riding your bike." and that as the US murder rate is four times that of the Netherlands you are "certainly more likely to be murdered while living in the United States than to die while biking in Amsterdam."

Note that Amsterdam is not all of the Netherlands. It's the largest city and quite busy and in fact it's probably one of the most dangerous parts of the country with regard to mopeds as well as other dangers. Most of the country, including Assen where we live, has a far smaller "problem" due to mopeds.

Something to complain about
To summarise, mopeds are one of the things that people get upset about in the Netherlands. But you have to put this in context. This country is very safe and there is very little to get upset about. A bit of perspective is required. What is complained about here are things that would not be complained about elsewhere. In fact, I'd go further than that: the Dutch quite often complain about things which in other nations might be a reason for boasting. You're not actually at any great danger from mopeds even though they are a nuisance and they are disliked by so many people. Nevertheless, mopeds need some control because this has become a subjective safety issue and I'd not suggest that other nations follow the Dutch example of allowing mopeds of any class onto cycle facilities because of that subjective safety issue.