Safer Streets: Design is Better Than Enforcement

As some American cities are attempting to reduce the number of car accident fatalities, under the umbrella of Vision Zero, the growing topic is one of traffic enforcement. Streetsblog has long documented many instances in which the police treats any case in which a car runs over a pedestrian as a no-fault accident, even when the driver was committing such traffic violations as driving on the sidewalk. In addition to enforcement, there’s emphasis on reducing the speed limit in urban areas, from 30 to 20 miles per hour, based on past campaigns in Europe, where speeds were reduced from 50 km/h to 30. Unfortunately, street design for lower speeds and greater traffic safety has taken a back seat. This is not the best way to improve street safety, and is not the standard practice in the countries that have reduced car accident rates the most successfully, namely the UK and the Scandinavian countries.

On high-speed roads, one of the most important causes of fatal accidents is the combination of driver fatigue and sleepiness. For some studies on this problem, see here, here, and here. The second link in particular brings up the problem of monotony: if a road presents fewer stimuli to the driver, the driver is more likely to become less vigilant, increasing the probability of an accident. One study goes on and shows that higher speed actually increases monotony, since drivers have less time to register such stimuli as other cars on the road, but this was obtained in controlled conditions, and its literature review says that most studies find no effect of speed. I emphasize that this does not mean that lower speed limits are ineffective: there’s evidence that reducing highway speed limit does reduce accident rates, with multiple studies collected in a Guardian article, and lower accident rates in France since the state installed an extensive system of speed cameras.

But while speed limit reductions offer useful safety benefits, it is important to design the roads to be slower, and not just tell drivers to go slower. Road monotony is especially common in the United States; per the second study again,

While comparing self-reported driving fatigue in the US and Norway, Sagberg (1999) suggests that the higher prevalence of self reported drowsy driving found in the US may be due to differences in road geometry, design and environment, as well as exposure. He argues that the risk of falling asleep is higher on straight, monotonous roads in situations of low traffic, where boredom is likely to occur. This type of roads is more common in the US than in Norway.

The studies I have consulted look primarily at highways and rural roads; I have not found comparable literature on urban roads, except one study that, in a controlled simulation, shows that drivers are better at gauging their own alertness levels on urban arterials than on rural roads. That said, urban arterials share many design traits that lead to monotony, especially in the United States and Canada:

  • They are usually straight, forming a grid rather than taking haphazard routes originating from premodern or early-industrial roads.
  • They are wide: 4-6 lanes at a minimum, often with a median. Lanes are likely to be wide, closer to 3.7 meters than the more typical urban 3 meters.
  • Development on them usually does not form a strong enclosure, but instead commercial developments are only 1-2 stories, with setbacks and front and side parking lots.

Such roads are called stroads in the language of Charles Marohn, who focuses on issues of their auto-centric, pedestrian-hostile nature. Based on the studies about monotony, I would add that even ignoring pedestrians entirely, they are less safe than slower roads, which prime drivers to be more alert and to speed less. It is better to design roads to have more frequent stimuli: trees, sidewalks with pedestrians, commercial development, residential development to the extent people are willing to live on top of a busy road.

Regarding lane width, one study finds that roads are the safest when lanes are 3-3.2 meters wide, because of the effects of wider lanes on driver speeds. A CityLab article on the same subject from two years ago includes references to several studies that argue that wide lanes offer no safety benefit for drivers, but are hostile to pedestrians and cyclists.

This approach, of reducing speed via road design rather than enforcement, is common in Scandinavia. Stockholm has a few urban freeways, but few arterials in the center, and many of those arterials have seen changes giving away space from cars to public transit and pedestrians. Thus, Götgatan is partly pedestrianized, and Odengatan has center bus lanes and only one moving car lane in each direction; the most important of Stockholm’s streets, Sveavägen, has several moving car lanes in each direction, but is flanked on both sides by medium-rise buildings without setbacks, and speeds are rarely high.

When enforcement happens, the great successes, for example in France under the Sarkozy administration, involve automation. Red light cameras have a long history and are controversial, and in France, Sarkozy lowered the speed limits on many roads and stepped up speed camera enforcement. The UK has extensive camera enforcement as well. Human enforcement exists, but is less common than speed cameras. Thus, the two main policy planks Vision Zero should fight for in the US are,

  1. Road redesign: narrower lanes, wider sidewalks, trees, and dedicated bus and bike lanes in order to reduce the number of car lanes as well as provide more room for alternatives. Zoning laws that mandate front setbacks should be repealed, and ideally so should commercial height limits on arterials. In central cities, some road segments should be closed off to cars, if the intensity of urban activities can fill the space with pedestrians.
  2. Lower speed limits in the cities, enforced by cameras; fines should be high enough to have some deterrent effect, but not so high that they will drive low-income drivers bankrupt.

It is especially important to come up with solutions that do not rely on extensive human enforcement in the US, because of its longstanding problem with police brutality and racism. The expression “driving while black” is common in the US, due to bias the police in the US (and Canada) exhibits against black people. In Europe, even when bias against certain minorities is as bad as in the US, overall police brutality levels are lower in the US by factors ranging from 20 to 100 (see for example data here). In my Twitter feed, black American urbanists express reluctance to so much as call the police on nonviolent crime, fearing that cops would treat them as suspects even if they are the victims. When it comes to urban traffic safety – and so far, Vision Zero in the US is an urban movement – this is compounded by the fact that blacks and other minorities are overrepresented in the cities.

This means that, in the special conditions of US policing, it’s crucial to prevent Vision Zero from becoming yet another pretext for Driving While Black arrests. As it happens, it does not require large changes from best practices in Europe, because those best practices do not involve extensive contact between traffic police and drivers.

Recall last year’s post by Adonia Lugo, accusing Vision Zero of copying policy from Northern Europe and not from low-income American minority communities. As I said a year ago, Adonia is wrong – first in her belief that foreign knowledge is less important than local US knowledge, and second in her accusation that US Vision Zero advocates copy European solutions too much. To the contrary, what I see is that the tone among US street safety advocates overfocuses on punitive enforcement of drivers who violate the speed limit or break other law. Adapting a problem that in Europe is solved predominantly with street design and technology (speed cameras don’t notice the driver’s skin color), they instead call for more policing, perhaps because mainstream (i.e. white) American culture is used to accepting excessive police presence.


  1. Scoop

    You seem to assume that lives saved by lower speeds justify increased driving time. Why? Clearly at some point the societal cost of slower travel would exceed the benefit of lower mortality. How do you know if you’ve reached it?

    • crazytrainmatt

      For those of us in cities where the majority do not drive, you can imagine that slowing traffic is all positive as congestion shifts trips to safer modes and thereby reinforces their broad political support.

      Either way, except for rural roads, the reality is that unsafe drivers are rarely getting from A to B much faster.

      • sonamib

        Either way, except for rural roads, the reality is that unsafe drivers are rarely getting from A to B much faster.

        That’s true. I bike a lot, and I’ve lost count of the number of times a driver has overtaken me with a tiny margin, at high speed, only to hit the brakes at the red light a few tens of meters later.

        But I’m not sure if it’s on point. Because some streets do need to be redesigned for slower speeds if we want them to be safer. Drivers will really go slower from A to B when the street is uncongested (going to a restaurant at night for example). You can maybe get some of that speed back by getting rid of some red lights, because if you’re driving slower it’s easier to yield for pedestrians and cars that have the right of way.

        And as you point out, slowing cars will also hopefully encourage people to shift to other transportation modes, which are safer and more efficient. It also tends to reduce sprawl, which has quite a big societal cost.

        • snogglethorpe

          Beyond what you mention, there’s also the advantage that road designs that slow speeds–narrower roads, more “containment,” less monotony–generally also result in a more pleasant environment to be in, especially for those not in cars.

    • lisadiaz

      You raise an interesting question Scoop. But I have to ask if you have any information about the societal costs of slower travel and how that might weigh in as more important than saving lives? I want to understand where you are coming from with your post. I am concerned that we would even try to compare the societal cost of slower travel to the value of human lives.

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  6. Colin V. Parker (@ColinVParker)

    Perhaps part of the reason the focus turns to enforcement is that when you broaden your concern from just safety to general pedestrian-friendliness, speed of travel is not the only concern. Obviously safety is the most important thing and as far as Vision Zero goes, I agree with you. But I would say that another concern is failure to yield at crosswalks, or when turning across a controlled intersection with a walk signal. Also general obnoxiousness like rapid acceleration and last-minute braking. At least according to Streetsblog, failure to yield is a small fraction (I’m estimating 1-2%) of total tickets. And I’m not sure if there is any real way to enforce other than by a human. My out-of-US experience is pretty limited, but it has been that failure to yield issues are much less prevalent. With your much more extensive experience, would you say that this is wrong, European drivers are just as unlikely to yield, or that street design also plays a big role there, or that European failure to yield enforcement is higher, or just a general cultural issue?

    I hear you on DWB, but I think it’s maybe worth drawing distinctions between issuing traffic citations, and making arrests and searches, with the latter two being where (I think) most of the issues are. That’s certainly where the big disparities seem to be. One could imagine unarmed officers tasked solely with citation issuance. Do such agents exist anywhere?

    • Adirondacker12800

      3,000 of them in Manhattan? They do a lot of parking violations but they do traffic too.

    • Matthew

      Camera and computer vision technology is good enough to enforce crosswalk laws, I believe, it’s just a matter of will.

      Regarding out-of-US experience, I would not group the UK with other European countries with regard to yielding behaviour. Here in the UK there is no culture of giving way to people walking when drivers make a turn, even though it is technically the law (albeit a law with loopholes so large you could drive a deadly lorry though them). There is a widespread — though false — belief among drivers that they are allowed to zoom around corners with nary a thought or even a look. And with the prevalence of blind corners (and blind driveways) in this country, it makes me wonder how the UK manages to do so well on certain safety statistics (my guess is that the relative smallness of the streets helps a lot).

      Most signalised junctions are very automobile-centric and are outfitted with (a) all-way stop, exclusive pedestrian phases summoned by beg button and long wait, (b) multi-stage crossings replete with staggered paths and caged islands, or (c) no infrastructure at all for people walking, who are left to sort out their own way in between phases for cars. There is also a common tendency to rely on simple give-way junctions or mini-roundabouts, providing a beg button-activated pedestrian-only signal (e.g. “pelican”, “puffin”, or “toucan” crossing) at some distance down the road if people complain enough to get one installed. Of course, those signalised pedestrian crossings are designed with sensors that will delay the pedestrian crossing until all approaching cars have passed by. On smaller junctions there are no pedestrian accommodations at all except the occasional dropped kerb for wheelchairs. The markings on the road are entirely car-oriented, and encourage drivers to roll through while completely ignoring any people walking. The famed Zebra crossing is a rare beast and almost never seen on the natural desire line but rather found in some off-line location to maximise inconvenience. Driver compliance with Zebras seems to vary by region, in some places the drivers are careful to always give way, and in others they don’t care.

      Really, it’s quite an evil and bizarre system that is a rather unwelcome surprise to foreigners when they first come here.

      • MR M CURRIE

        Yet the Uk has some of lowest rates of Pedestrian and Road User deaths in the World. So maybe your assessment of this evil system is shall we say a little over the top.

        There may be many factors in play here.

        The UK has strong programme to reduce urban road speeds, as the lower the speed the more likely a driver is to stop in time for a pedestrian and also reduce the consequences of being hit.

        The UK has long had a central government fund to local authorities for small scale junction improvements that are designed to reduce accident rates and the impacts from accidents.

        Parking is highly controlled in the UK and since most main roads are narrow there is little parking on these roads. I know some used to the American experience think parked cars provide a buffer between pedestrians. But my child road safety training as a child stressed not trying to cross the street between parked cars because of reduced sightlines. You or the driver can’t see the other until you have entered the road, a street with no cars parked means both can judge speeds of vehicles/whether a pedestrian is about to cross ahead of them.

        There is no such thing as jay walking law in the UK , you can cross where ever you think it is safe to do so. Drivers in the UK are used to people crossing in the middle of the street, it also means a pedestrian accident is never written off as they were jaywalking. Drivers are presumed to operate with due care and attention. Scene of crime officers will attend all serious street accidents where to record tire marks and take other foresnic evidence. Woe betide you if you were speeding, they’ll work out if you could have stopped in time.

        Of course it may be a lot of these ‘evil’ pedestrian schemes actually have a purpose and do make a difference.

        • Matthew

          It’s probably true that the speed reduction campaigns (twenty is plenty) and the relatively small streets of most places have helped. But other than that… well…

          Yes, there is little designated parking on many streets, especially high streets where you’d expect to find it. But that does not stop drivers from parking! Most places are clogged up with pavement parking (sidewalk parking) blocking the footpath so that people are forced to walk in the carriageway with motor vehicles anyway. Please tell me how this has a purpose and is making a difference. Do you live or visit in the UK, particularly outside of London? If you did, you would know how widespread the scourge of pavement parking is. In London, at least, they have special laws that allow the police and civil enforcement to take action against pavement parking. But outside of London, the police won’t lift a finger, and civil enforcement is powerless to stop it. Drivers park on the pavement with impunity all over the country (besides London, where maybe something might be done about it) and block up the footways, making life miserable for people walking (especially if disabled).

          It’s true that the UK does not have laws against ‘jaywalking’ but that’s about it. They are quite happy to say that you can cross anywhere you like, but you’re on your own trying to dodge the drivers. It’s rare to find a crossing where you need it. And the drivers do not stop. I have witnessed families and people with disabilities get stranded on one side of the road, fruitlessly waiting for traffic flow to lighten up. Sometimes they get frustrated, and if they can, they make a sudden dash across the street whenever a slight gap appears. It’s scary to watch. I have seen a couple nearly killed this way, as they attempted to dash across a typical London street with no crossing provision, only to come face-to-face with the grill of a suddenly stopped SUV that was making a turn. I have lost count of the number of times I have witnessed a person walking doing a strange dance on the kerb where they hop back and forth numerous times, not quite sure yet if they can safely cross without getting run over by a car, changing their mind 3 or 4 times before finally sprinting to the other side. There’s so much fear in such a simple act: crossing the street. There’s something deeply wrong here.

          Doing this day in and day out must be very tiring. I would not be surprised at all if part of the UK’s statistical ‘success’ came from people simply choosing not to go walking at all; staying at home or getting in a car instead. We could have zero pedestrian deaths tomorrow if we prevented everyone from ever walking anywhere, but I think that you would agree that would be a policy failure to the highest degree!

          You are much more confident in the workings of the justice system than I am. I know that many crashes and incidents go unreported, and I have that fact from the officials at the county and the city who are equally skeptical of the reported numbers. Even going by the recorded cases, It doesn’t take long to glance at the papers and find the latest outrage: every week it seems, brings yet another driver who is not even charged by the police with causing death through careless driving. There’s even the case of Michael Mason, who was killed in a rear-end collision by a negligent driver, and the police have entirely declined to prosecute thus leaving the family to fundraise for a private prosecution! (Bizarre society, this one). What would you say to the family of Ying Tao in London? She was crushed by a left-turning lorry driver who simply failed to look. Despite extremely clear & gruesome video evidence (which has been widely publicised) the police have turned down that case as well. I could keep going, since dozens of high profile cases come up every year. It is rare indeed that anyone is ever prosecuted for dangerous driving, albeit I agree that it does happen sometimes (probably more so than in the USA). But even after the verdict is reached, the punishment can often be a joke. The police caught some reckless man doing 150 mph on county roads near me this past summer, and guess what his punishment was? Loss of driving privileges for approximately 2 months! Absurd! If that’s what happens, I can understand why many police officers may be cynical at this point.

          • Adirondacker12800

            There was a really weird statistic, I don’t know how true it was, published years ago. A quarter of all pedestrian deaths in the U.S. occur in New York City…… wide swaths of the U.S. don’t have any pedestrians. It’s difficult to run them down if there aren’t any. Greater London is going to be high. There’s actually pedestrians there.

    • Alon Levy

      I’d argue it the other way: the more the focus is on general pedestrian-friendliness, the more design matters and the less enforcement matters. On Thayer Street in Providence, drivers yield to pedestrians. Elsewhere in Rhode Island, they do not. The difference is that Thayer Street doesn’t give cars enough space to move fast, and once cars are slowed down, pedestrians cross fearlessly and drivers are compelled to yield. Trying to enforce failure to yield laws instead of designing around them just reeks of selective policing to me.

      In Stockholm, I don’t know how much drivers yield, because I never had to be in position to find out in the first place. Important intersections are signaled, and less important ones don’t have much car traffic in the first place.

  7. Ian Mitchell

    “but not so high that they will drive low-income drivers bankrupt.”

    Why not?

    Is there any compelling argument for people who can’t really afford cars (who might not make rent if they get a flat tire or a belt somewhere snaps), being allowed to drive poorly without similar penalties?

    Part of the reason political will fails to make decent bus systems in so much of the US, is that car ownership costs are reduced by various subsidies, obscured by financing, and so every poor person aspires to having a car, any car, because it can save them often as much as 10 hours per week, taxi costs (in small and mid-sized towns, poor are the largest source of taxi trips).

    If car ownership was well outside of the budget, there would be a source of political will for good transit. Maybe even good enough for people who own cars to use.

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