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.

Reducing speeds in villages. Britain vs. The Netherlands

View Larger Map

When we were in Britain last October we drove from one of our parents to the other. It was an interesting experience being back on Britain's roads and making a long journey by car. One of the things we especially noticed after our absence from Britain's roads was how attempts had been made to limit speeds on roads through villages, but that they were inadequate. Speeds remained too high, and conditions for cyclists and pedestrians remained unpleasant.

The example above is of the A153 entering the village of Coningsby in Lincolnshire, and that's the example I'll use in this blog post. There are hundreds of villages along similar roads in the UK. but this is the one by which I stopped and took some photos:

Dangerous British example: Cycle on the road through a pinch point with 40 mph (64 km/h) motor vehicles.

The national speed limit of 60 mph ( 100 km/h ) applies along most of the length of the A153. On entering the village this falls to 40 mph ( 64 km/h ). A reduction in speed is encouraged by signs and a central reservation which doubles as a space for pedestrians to cross the road, though there there is nothing other than grass verge to walk on if you reach the other side of the road.

The A153 has no parallel cycle or pedestrian path. Anyone who wants to travel the 4.5 miles between the next village, Mareham-le-Fen and this one has to use the road. Many journeys are made between villages separated by this sort of distance in order to shop, use sport facilities, go to school or to commute. Coningsby is a desirable destination from Mareham because there are more shops and other facilities in this larger village. However, because cycling along here means being overtaken by vehicles travelling at 100 km/h, very few people would consider it. We stopped for several minutes to take these photos and no cyclists or pedestrians were seen. Everyone who was making this journey made it by car, van or truck.

Where there are two vehicles heading in opposite directions, there is very little room for a motorist to overtake a cyclist.

A few metres past the 40 mph speed limit signs there is a central reservation. It is narrow and does not require drivers to divert much from a straight line. Many vehicles are still travelling in excess of the speed limit when they reach this point. Calls can be made that drivers should slow to well below the speed limit when passing a cyclist inside the pinch point, but they won't be heeded. The result is that anyone on a bicycle will be passed extremely close by a motor vehicle which arrives in the same place at the same time. This does not make for a pleasant or safe experience when cycling. Alternatively, the cyclist can "take the lane" and attempt to force motorists approaching from behind to brake sharply, but this also is doesn't make for pleasant or safe cycling and causes resentment amongst drivers.

This design of road, and this design of traffic calming, is lethal. What's more, given the high speeds that remain through the village, it doesn't even result in particularly pleasant conditions for those who live there.

The reason why this particular feature of the road grabbed my attention was that a few days previously I'd pointed out something very similar in concept to the study tour group from Vilnius when they visited us in Assen.

If you had heard only a description of these two roads and not seen the physical reality then they would probably sound like almost the same thing. However, they are not the same in practice. Here is the "equivalent" traffic calming design in Assen:


Grotere kaart weergweven

The Witterhoofdweg has a speed limit of 60 km/h ( 37 mph ) before the signs and 30 km/h ( 18 mph ) through the village. This is the speed limit through most villages in this area. A third of the Dutch road network now has a speed limit of 30 km/h or lower.

Safe Dutch example: Speed limit is 30 km/h (18 mph) and cyclists have a completely separate cycle-path rather than riding through the pinch point with motor vehicles

The central reservation is much larger than the British example and requires drivers to change course quite dramatically as they drive around it. You couldn't drive through here at the speeds at which drivers in Britain routinely enter Coningsby.

The reservation is 4.5 metres wide, meaning there is ample space in which to wait to cross the road even with a loaded bicycle. On the other side of the road there is a cycle-path which you may well want to reach. Now how on the left side of the photo you can see the three metre wide cycle-path which continues the entire length of the village, even though the speed limit on the road is 30 km/h. At junctions with side-roads in the village, the cycle-path has priority. This results in a continuous, convenient and stress free experience for cyclists.

Looking in the opposite direction we get a good view of the cycle-path as it enters the village. The complete separation of cyclists and drivers ensure that making cars swerve to slow them down doesn't in any way endanger cyclists passing this point at the same time.

For most of the distance from Assen the cycle-path is separated by too large a distance from the road for it to easily appear in photos taken from the road. This cycle-path is four metres wide.

At the opposite end of the village there is a similar traffic calming construction. Cyclists retain a very good degree of subjective and actual safety right through this village and out the other side.

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At the time when we took this photo it was a cold winter day in the Christmas holidays. However, there was a regular stream of cyclists, as there always is. When the schools are in session, this is part of a route taken by thousands of children each day who ride their bikes from villages to the South West of Assen into the city. Witten, where these photos were taken, is just 3.6 km from the centre of the city. However, this is merely the half way point to the next village, Bovensmilde, which is 6.6 km away - almost exactly the same distance as Mareham-le-Fen to Coningsby, and many people travel along here by bike from other villages considerably further away than that. Because the distance can be covered on cycle-paths, the experience will be pleasant and safe when doing so, and it's convenient to cycle, people cycle.

Written descriptions of these two traffic calming devices would sound the same. However, in reality they are different. Aerial views of both traffic calming features to the same scale:


Coningsby. The signs are above the top of this view, the central reservation is just behind the truck. No need to divert at all while driving through here. While there is space for a cycle-path, none has been built  - View Larger Map


Witten. The signs are very close to the central reservation (see shadows to the right), motorists have to divert from a straight line to cross this point. Cycle-paths lead in all directions, all separated from the road, some by a considerable distance - Grotere kaart weergeven

Now I expect some readers to point out that the A153 is a larger more strategic road than the Witterhoofdweg. They'd be right of course. But larger roads in the Netherlands have rather more care taken to preserve the rights of cyclists and pedestrians to go about their everyday business in peace, not less. A traffic calming feature like this simply has no place on a busy road like the A153.

In Britain, the same ideas have been used as in the Netherlands, but they are often applied in a much weaker way, and often in staggeringly inappropriate places. That is what the blog posts tagged "lost in translation" show.

What are streets for ?

This is what the street right outside our home looks like this evening. The local children have been playing hopscotch. Anyone on the way in or out by bike or in a car has to take care around the children. No parental supervision is needed.

Sometimes the chalk paths and buildings made by the local children stretch all the way down our street and around the corner into the next. Children ride back and forth on a variety of different devices, or run up and down.

Ball games are also encouraged by a goal on the green outside our home. No injuries, damage to property or car crashes have been reported as a result.

Our home is in the middle of the google maps image. You'll see how these houses are built around a small green with a little playing equipment. The message is quite clear. The street is not merely a space for cars, it's a space for children to play. For people to socialise.

On New Year's Eve, one of the neighbours put up a tent so all could get together and socialise in this space.

This is a quite typical example of planning of a residential area in the Netherlands in the early 1970s (our home was built in 1972). The same principles are still applied, with the same results.

A later blog post shows an example of a hopscotch game built permanently into a road in a residential area.

A Cul-De-Sac ? Isn't that "bad" ?
Like everywhere else in Assen, and indeed across the nation, whether cul-de-sac like this or another street design, all residential streets are connected to the finely spaced grid of very high quality cycle-routes which cover the Netherlands. There are two high quality cycle-paths, both four metres wide, within 200 m of our home. These take us to every destination. There is no single design of residential street which discourages cycling and walking, it's the lack of a decent network of cycling facilities and the lack of subjective safety on the roads which do exist that cause the problem.

Both areas feature on the Study Tours that we organise in Assen.

Traffic calming the countryside

In the Netherlands, rural roads are also a pleasure for cyclists. The reason is that there are very few cars using them. Many rural roads only offer convenient through routes by bicycle. Drivers are encouraged to take other routes.

The signpost to the left stands in the village of Peize, which has just over 5000 residents. It is fairly typical for rural areas. Note that there are directions given to 9 different places by bike (the red writing on a white background), but drivers are offered only "all directions" (white writing on a blue background).

What happens if the drivers try to follow the cycling route ? Well, it's not easy. Fairly frequently these routes are not passable at all if you're driving a car. For that reason, drivers are better off using the directions indicated for them, even if it will mean a detour. On the way into this village I used the route indicated left on this sign to Eelde-Paterswolde. That means the road shown in this video:

Explanatory captions on this video are visible only on a computer and not on a mobile device

On the way out of the village, in the direction the camera is pointing in the photo at the top, I used this one:

Explanatory captions on this video are visible only on a computer and not on a mobile device

There are 29000 km of cycle path in the Netherlands and 130000 km of road. What is often not understood outside this country is how much of the "road" is also (almost) only for bikes. Motorists can only follow the motoring routes, not the cycling routes. As a result, the majority of country roads are almost like cycle paths in all but name. The experience of riding along them is almost completely free of cars.

There are many other examples of smooth cycle paths next to (deliberately) rough roads.

Not just the towns, but also the countryside has to a large extent been "traffic calmed". Sections of road joined by cycle path make through routes for cyclists, not for drivers. It makes cycling a pleasure.