Archive for the ‘Drivers’ Category

From an interesting op-ed, in which I am quoted, in The Canberra Times:

Not long after Henry Ford drove the car into mainstream American life, a new area of psychology began to flourish. Its aim, in layman’s terms, was to understand why apparently normal people become complete arseholes behind a steering wheel. Leon Brody’s 1955 book, The psychology of problem drivers, concluded that ”problem drivers are problem people; or rather, people with problems, including problems of which they often are not aware”. Until then, researchers had believed most crashes were caused by physical shortcomings such as slow reflexes, poor eyesight and glare-recovery time. But, as Herbert Stack wrote in the Bulletin of the New York Academy of Medicine in 1956, ”[In] all of our studies, these characteristics have been found to have little significance. The real causes of accidents are far more deep-seated. They have to do with our attitudes, our emotions, and our judgments.”

Bus companies say that women drivers are ‘better’ than men drivers, and seek exemption from equal opportunity and anti-discrimination legislation in order to advertise exclusively for women trainees. Women are reported to be ‘gentler’ on the buses, and rather than simply driving on when mechanical failure presents, call in the problem to the depot. This prevents the escalation of damage with consequently higher cost of repair. As for public relations, according to bus companies, women also ‘relate better’ to passengers.

One of an interesting number of points in an op-ed inspired by the campaign by women in Saudi Arabia for the right to drive.

(thanks Alan)

My latest Slate column is up, examining the problems with “Children at Play” traffic signs (the headline, which is never the writer’s, may overstate things a bit…)

If the sign is so disliked by the profession charged with maintaining order and safety on our streets, why do we seem to see so many of them? In a word: Parents. Talk to a town engineer, and you’ll often get the sense it’s easier to put up a sign than to explain to local residents why the sign shouldn’t be put up. (This official notes that “Children at Play” signs are the second-most-common question he’s asked at town meetings.) Residents have also been known to put up their own signs, perhaps using the DIY instructions provided by eHow (which notes, in a baseless assertion typical of the whole discussion, that “Notifying these drivers there are children at play may reduce your child’s risk”). States and municipalities are also free to sanction their own signs (hence the rise of “autistic child” traffic signs).

There was an assertion made in one of the letters (signed by Louise Hainline, Norman Steisel, and Iris Weinshall in response to a recent New York Times editorial on cycling that caught my eye:

When new bike lanes force the same volume of cars and trucks into fewer and narrower traffic lanes, the potential for accidents between cars, trucks and pedestrians goes up rather than down. At Prospect Park West in Brooklyn, for instance, where a two-way bike lane was put in last summer, our eyewitness reports show collisions of one sort or another to be on pace to be triple the former annual rates.

The first point is that while the PPW conversion did take away one travel lane, the width of the existing lanes was not altered. So there may be fewer lanes, but they are not, as the letter argues, “narrower.” It may be that entire street feels narrower, which, as an emerging school of what I’ll call ‘behavioral traffic calming’ argues, is actually a good thing. Drivers, as I’ve quoted Ezra Hauer as saying, “adapt to the road they see.” They either do not see traffic signs or fail to read their meaning correctly. If they see a wide open, long boulevard, they will drive like this.

Even if the lanes were narrowed, as John LaPlante recently argued in the journal of the Institute for Transportation Engineers, “there is no significant crash difference between 10-, 11-, and 12-foot lanes on urban arterials where the speed limit is 45 mph (or less).” (a finding, he notes, that was unfortunately left out of AASHTO’s recent Highway Safety Manual).

And there’s something deeply suspicious about that “eyewitness reports” note; were they actually out there, day after day, meticulously logging conflicts and crashes (tellingly, they make no note of severity)? And why, if everything was so great with the street before, were they even doing these “before” counts? As the case of roundabouts shows, what people perceive as individual danger often does not translate at all to an increase in overall risk; in fact, it’s quite the opposite.

But let’s take that notion — that fewer and narrower lanes lead to more crashes. This is a staple of traffic engineering, and in fact it does have some validity — when applied to highway environments (which PPW at times unintentionally resembles). Even here, though, the effects are often not ‘statistically significant’ and ‘more complex than expected.’

But in non-highway environments, there’s all kind of evidence that reducing the number of lanes (a.k.a. the ‘road diet’) can have positive safety benefits. As the Federal Highway Administration has noted:

Road­ diets­ can­ offer­ benefits ­to­ both ­drivers ­and­ pedestrians… road diets may reduce vehicles speeds and vehicle interactions, which could potentially reduce the number and severity of vehicle-to-vehicle crashes. Road diets can also help pedestrians by creating fewer lanes of traffic to cross and by reducing vehicle speeds. A 2001 study found a reduction in pedestrian crashing risk when crossing two-and three-lane roads compared to roads with four or more lanes.

But what if one of those lanes your crossing is a bike lane? Surely that must make things less safe, no? More interactions in less space. In a forthcoming paper to be published in the Journal of Environmental Practice Norman Garrick and Wesley Marshall examined 24 California cities (12 with relatively low traffic fatality rates, 12 with relatively high rates). They found that the cities that had a higher bicycle usage had a better safety rate, not just for cyclists but all road users. They write:

Our results consistently show that, in terms of street network design, high intersection density appears to be related to much lower crash severities. Our street design data also contains strong indications of these trends; for example, the high biking cities tend to have more bike lanes, fewer traffic lanes, and more on-street parking. At the same time, large numbers of bicycle users might also help shift the overall dynamics of the street environment – perhaps by lowering vehicle speeds but also by increasing driver awareness – toward a safer and more sustainable transportation system for all road users.

And as Eric Dumbaugh, of the University of Texas A&M, notes, “most recent research reports that wider lanes on urban streets have little or no safety benefit, at least to the extent that safety is measured in terms of empirical observations of crash incidence” (e.g., Potts, I.B., Harwood, D.F., & Richard, K.R. (2007). Relationship of Lane Width to Safety for Urban and Suburban Arterials. Transportation Research Board 2007 Annual Meeting; Milton, J., & Mannering, F. (1998). The relationship among highway geometries, traffic-related elements and motor-vehicle accident frequencies. Transportation 25, 395–413; and so on).

But the authors of this letter are not trafficking in empirical evidence, even as they allege that the NYC DOT’s data “more puzzlement than enlightenment.” It’s unfortunate that this letter is signed by a former DOT commissioner, and an academic — who should both know that it is evidence and analysis, not vague “eyewitness” reports and random testimony, upon which good science, planning, and safety interventions are made.

And as always, curious to hear of more work either supporting or countering what I’ve said here.

A number of readers (one is always heartened to discover they exist!) have written in to ask about the ongoing state of this blog, which has admittedly declined in frequency as of late. I am still here, I assure you, but there are several things at work here: 1.) I’ve shifted most of the micro-announcement, interesting-links sort material to Twitter (follow here); my column at Slate.com, meanwhile, covers some of the longer-form material that may otherwise have been treated here. 2.) I’ve had a large number of magazine and other journalistic assignments, some having nothing at all to do with driving or transport, and in the economy of words, paying work must always trump non-paying (and trust me, if this blog was a paying gig there’d be no problem filling it seven days a week with material). And, 3.) I’ve been traveling a lot, for work and for pleasure.

I’ve just in fact returned from Lisbon to find a new paper from Michael Sivak in my inbox (“Toward Understanding the Recent Large Reductions in U.S. Road Fatalities,” in Traffic Injury Prevention), the third of a trilogy of works examining the recent drop in U.S. traffic fatalities; this paper uses the most updated data available, from 2008. As he notes:

From 1994 to 2005, U.S. road fatalities increased by 7 percent, from 40,716 to 43,510. However, from 2005 to 2009, they dropped by 22 percent, to 33,963 in 2009 (see Figure 1). A reduction of such magnitude over such a short time has not occurred since road safety statistics were first kept (starting in 1913), except for the reductions during World War II (National Safety Council 2009).

He essentially finds the decline is greater than might be expected were we simply to factor in the state of the economy over the past few years, and the chart below summarizes where injuries have gone up and where they have gone down in a number of significant categories. There’s other intriguing details — like the decline in repeat DWI crashes, or the downtick in station-wagon crashes — but I’ll leave those for you to sift through.

This Ad Age report cites a substantial decline in young drivers (and driving), and chalks it up largely to the “digital revolution.” Perhaps, but conspicuously underplayed is graduated drivers licensing programs, which have made driving (solo, at any time) at age 16 or 17 a thing of the past in many states (with good reason).

(Flash of the headlights to Clive Thompson)

As I’ll be going to Australia later in the year, I suppose it’s a good thing I was made aware of a bit of slang: Bogan. Apparently it’s a bit like a “chav” in the U.K. I don’t know how the term is actually received in Australia, but if any readers want to weigh in…

And, this, according to the website “Things Bogan Like,” is how a bogan drives:

While the bogan generally engages in few critically important activities and has accrued a lifetime of missed deadlines, when on the road it is in an urgent hurry. If delayed by a stop sign, it will charge through. If delayed by a line of traffic, it will seek to drive in the emergency lane. It will reach its destination a full 90 seconds earlier than the non-bogan, and it will consume that 90 seconds, along with 300 other seconds, to stake out a parking space that is 30 steps closer to Boost Juice.

If the bogan’s anger becomes moderate, it will scream from inside its car, and make obscene gestures. It is unlikely to realise that the other person cannot hear its profanities from inside their own car, but this does not deter it from pursuing this action with vigour. If the anger level becomes high, the bogan will attempt to overtake the other car without indicating, expecting surrounding cars to part like Katie Price’s legs. If it is not allowed to re-enter its original lane, it will emerge from its car in a blind fury. The alpha road warrior bogan will attempt to lure the other driver from their car with an elaborate roadside war dance, intermittently spitting and kicking door panels. If this is not successful, it will eventually return to its car, do a burnout, and rocket off into the distance, which is usually the next traffic light 100m up the road.

(thanks Alex)

Via Nudge, a small rental-car reminder of road directionality for tourists (the reversion to old norms is an actual risk issue, one that presumably can supplant the heightened sense of awareness due to a new environment).

The comparison here is of course to London’s street warnings to “look right,” etc.; I’ve often wondered about any before-after numbers (though they’ve been in London for many decades, no?) about their effectiveness as, for example, other places with left-side directionality don’t feature the warnings.

The genetic correlates of bad driving.

(thanks Peter)

Daniel Pink points me to an interesting new study via NBER: “Traffic Congestion and Infant Health: Evidence from E-ZPass,” by Janet Currie and Reed Walker.

The abstract states:

This paper provides evidence of the significant negative health externalities of traffic congestion. We exploit the introduction of electronic toll collection, or E-ZPass, which greatly reduced traffic congestion and emissions from motor vehicles in the vicinity of highway toll plazas. Specifically, we compare infants born to mothers living near toll plazas to infants born to mothers living near busy roadways but away from toll plazas with the idea that mothers living away from toll plazas did not experience significant reductions in local traffic congestion. We also examine differences in the health of infants born to the same mother, but who differ in terms of whether or not they were “exposed” to E-ZPass. We find that reductions in traffic congestion generated by E-ZPass reduced the incidence of prematurity and low birth weight among mothers within 2km of a toll plaza by 10.8% and 11.8% respectively. Estimates from mother fixed effects models are very similar. There were no immediate changes in the characteristics of mothers or in housing prices in the vicinity of toll plazas that could explain these changes, and the results are robust to many changes in specification. The results suggest that traffic congestion is a significant contributor to poor health in affected infants. Estimates of the costs of traffic congestion should account for these important health externalities.

I’ve not read the paper yet (if anyone has a PDF I’d love to see), but one interesting question is whether this is longitudinal as well — were the rates tracked before and after the introduction of EZ-Pass? And would this vary depending upon the number of lanes that actually offer EZ-Pass (roughly half at most NYC-area toll plazas). A provocative thesis in any case, coming on the heels of David Owens’ interesting piece in the WSJ.

Congestion isn’t an environmental problem; it’s a driving problem. If reducing it merely makes life easier for those who drive, then the improved traffic flow can actually increase the environmental damage done by cars, by raising overall traffic volume, encouraging sprawl and long car commutes. A popular effort to curb rush-hour congestion, freeway entrance ramp meters, is commonly seen as good for the environment. But they significantly decrease peak-period travel times—by 10% in Atlanta and 22% in Houston, according to studies in those cities—and lead to increases in overall vehicle volume. In Minnesota, ramp metering increased overall traffic volume by 9% and peak volume by 14%. The increase in traffic volume was accompanied by a corresponding increase in fuel consumption of 5.5 million gallons.

One thing I’d be curious to know about the papers Owens’ cites is whether the introduction of ramp metering simply brought more vehicles back to the metered-facility, and away from other roads they may have been traveling on (perhaps those were covered in the “overall vehicle volume,” but it typically seems smaller roads are not as well measured in those terms compared to highways).

That might be useful, but a compelling study has already revealed that teens taught to drive by their parents are 2.7 times more likely to get into a fatal accident than those who take formal driver’s ed courses. The 2007 study focused on Texas and was funded by the National Highway Traffic Safety Administration.

This via an interesting article on reforming driver’s ed in Texas.

Unlike most big city mayors (Portland’s Sam Adams is, or was, or still is, an exception), D.C.’s Adrian Fenty drives himself, and is apparently not setting the best example:

But Fenty’s recent fender bender has again raised questions about why the mayor is commandeering his city-issued vehicles, a Lincoln Navigator and a Smart Car. Fenty (D) was driving the Navigator when it collided with a Nissan Pathfinder at a four-way stop in the Chevy Chase neighborhood of the District this month. A police report on the accident was incomplete and contradicted an accounting of the incident provided by the mayor’s office.

It is another controversy surrounding Fenty and his vehicles. In May, he apologized for allowing a friend who was not a government employee to drive the Navigator, an apparent violation of the law. Fenty also picked up a speeding ticket in the Smart Car during the same month.

Looking at this page of state-by-state laws on texting and various forms of phoning while driving, compiled by the Governors Highway Safety Association, I was intrigued to note a column reserved for the drivers of school buses, and that a number of states (16) have a law prohibiting them from any form of phone use — even when that state does not actually ban the use of a hand-held device. Only one state at the moment actually prohibits school bus drivers from texting while driving, an example of how quickly the technology and practice has arisen.

But the school bus driver distinction is an interesting one to me; are we saying that is not OK for the drivers of vehicles carrying our children to talk on the phone and drive, and if so, why? But if this is not OK, then why is it OK for the drivers of every other vehicle around that bus to be talking on the phone, and why is it OK for parents with their kids in the car to talk while on the phone? I think this ties in to a certain feeling we have about risk: We worry about being in someone else’s hands (even a school bus, statistically safer than private transportation), but maintain a feeling of what’s been called “the illusion of control” when we are the perceived masters of our own fate.

I had come across the above slide, via a post at Kottke’s blog, and it is taken from a talk by a Harvard University researcher named Lant Pritchett. I was intrigued by the progression Pritchett had theorized in the way that once-seemingly controversial issues (his slide illustrates changing attitudes over interracial marriage) had, over time, simply become part of the normal state of affairs. Now, clearly this is not always a linear, teleological dynamic, but it’s interesting to try and think of other examples where it applies (a woman’s right to vote, recycling, smoking is bad for you, etc.).

I was also interested in what areas of traffic safety and the larger culture of traffic to which it might apply — seat belt usage, for example (or the idea of laws for same), driving while drunk, motorcycle helmets (or helmets in hockey and other sports), etc. And I found myself reaching for the concept in a recent column for Reclaim, the magazine of NYC’s Transportation Alternatives (of which I’m a member; if you think, by the way, that this makes me some anti-car radical, I’m also a member of AAA). The column was prompted by some recent commentary in the press, in light of the recent closing to traffic of a few blocks of Broadway in Times Square, that the NYC DOT was running a series of “elitist” reforms.

Whether this would in and of itself be a bad thing is another issue altogether — for all kinds of civic reforms we now take for granted and that make cities livable places began as the work of progressive “elites” — but I took exception with the idea that programs meant to benefit pedestrians and transit users, who represent by far the majority mode of Manhattan, were “elitist” policies causing harm to some disenfranchised majority of New York car users. But I am interested also in the reception of this and other projects via Pritchett’s evolution; in certain quarters of the media, they have been branded in the “silly” and “controversial” vein, though as this “Q Poll” indicates (the poll found early support for the Times Square project, support that might rise if the media didn’t always frame the story so negatively, or if the project’s benefits were explained to more people), we might already be moving closer to obvious.

In any case, the essay is here, or after the jump.

(more…)

I know the driving age is low in some Western states, but this is ridiculous.

In the issue of the London Review of Books that just arrived in my mailbox, I opened it to find this extraordinary passage by Andrew O’Hagan, which magnificently encapsulates the existential pleasures of driving (he deals with some of the ambivalence later). The piece goes on to say a few kind words about some recent books, including my own.

Behind all this stands the culture of driving and the fact of traffic. We love driving and we hate it, we praise it and we slate it, but our relationship with cars is a lively element in our relationship with ourselves and other people. The downturn in the industry chills us, but mainly because – and we don’t feel this way about pharmaceuticals or petrochemicals – it makes us imagine we might have to stop being who we are. I speak as a fairly late convert to the life-enlarging potential of cars: for 36 years I was happy to go around the country on buses and trains, taking the Tube to any destination I ever wanted or needed to visit, to work and to cinemas, on dates and on expeditions, without ever feeling at a loss. When I took taxis it was just another form of being in the hands of others. It meant listening to speeches I found actively aggressive and paying over the odds for the privilege. Then I began taking driving lessons and the world suddenly opened up to me in a way I now depend on. The first long drive I took after I passed my test was a kind of baptism: I put down the windows and let all life’s unreasonable demarcations fly behind the car, enjoying the illusion that I now had a friend who cared for my freedom.

So far, so sad. And so far, so essential…

There’s a curious discussion over on the bulletin boards of the Smart car owners site, oriented around the question of whether the drivers of other cars consider it an insult to be passed by a Smart car. Apparently the phrase “passed by a Smart” is highly Google-able.

Most theories seem to revolve around other drivers not considering the Smart a “real car” — i.e., they take umbrage when the smaller vehicle passes them (masculinity issues or some such), or the site of the small car hurtling along at an “impossible” speed makes them think they themselves must be driving slowly.

When I drove the smart in NYC, I found two general reactions: Versions of the above, and then outright, gushing approval (typically from pedestrians, though, more from other drivers). Sometimes people would seem to be upset that I had passed them, as they would then rev their engine to pass. As a side note, I occasionally witness this on a bike as well — drivers desperate to get ahead of me, even as we approach a red light (but a bike will always win because a car has to begin braking sooner, and because a bike can ride in the space in-between of course), almost as if they were trying to valiantly justify their automotive choice, or reclaim its presumed velocity advantage.

(Horn honk to Rick)

At the CTS conference yesterday at the University of Minnesota, I was chatting with a traffic engineer who relayed an interesting anecdote. As a traffic engineer, he is used to addressing packed rooms of people, all filled with firmly held convictions on the way things should be done. He was chatting with a colleague, a civil engineer, about whether people ever offered any input at meetings concerning things like sewer systems. The answer was no.

It should be said that I’m of the opinion that, particularly in some local jurisdictions, community residents might actually have a better idea of how to control their streets than engineers working with standardized approaches; and that, too often, streets are merely viewed as sewers of a sort, channels for simply moving as much stuff — i.e., cars — as possible, with insufficient thought for other considerations.

But the engineer also had a quite valid point, which beleaguered traffic engineers face every day at town meetings across America when trying to, say, tout the benefits of a roundabout. Suddenly, there will be a volley of criticism: Those things are dangerous, they will make traffic worse, etc., despite all statistical evidence to the contrary. Of course, people offering these opinions typically never have actual evidence, nor have they studied the problem in depth, and yet they feel comfortable to make diagnoses on engineering problems which it seems they would not feel comfortable doing in any other arena.

I thought of this morning when reading a dispatch on how Kansas City is going to introduce ramp metering to its highways (thanks Bryan).

This, not surprisingly, prompted a letter in the local paper:

Metering entrance ramps to I-435 is a terrible idea (5/13, National/Local, “Engineers turn to ramp meters to ease gridlock”). I travel to Milwaukee several times a year, and they have metered ramps onto I-94. They slow traffic down, especially during rush hour.

People who live in Milwaukee and drive on the interstates hate them. Each time I drive up there I can’t wait to get back to Kansas City, where we know how to let people get around.

Ramp meters, as I mention in Traffic, are a particular case where the individual windshield perspective of drivers cannot account for the larger flow of the traffic system, with its multitude of variables; user optimality trumps system optimality in the mind of the driver. As one engineer told me, people ask me, why are you stopping me, the highway’s moving? The highway’s moving because we’re stopping you.” But hold on, K.C. engineers, throw out those models, rip up those studies — we’ve got a driver who “travels several times a year to Milwaukee,” where “everybody” hates ramp meters (everybody, except, presumably the people who are moving more smoothly than they would be without them). But there is “room” on the highway for people to enter, this driver notes. “Room,” or “capacity” as engineers might more properly say, is, alas, not the only variable to consider in highway flow, and indeed, squeezing another driver into that “room” might disrupt the flow, pushing the stream past its critical density, plunging the system from a congested synchronous flow into stop-and-go congestion. Of course, some ramp metering schemes do send traffic back up the ramps — but one might also note that those ramps might typically be backed up already, and that in some cases this is actually made worse without ramp meters. And I need hardly point out that one cannot judge the success or failure of a ramp metering scheme simply by judging one on-ramp at any one time — rush-hour traffic on a congested urban system is an incredibly complex array of networks and flows that are well beyond the ability of any one driver to fully intuit what is going on.

On a bus trip in Tokyo, I was surprised to occasionally glance down and see, in a neighboring car, a television screen playing where the nav device might normally sit. Apparently this is a favorite of taxi drivers in a number of other Asian capitals.

The distraction effects of a front-mounted television are obvious. But what about the televisions in the back seats of other vehicles? We’ve all seen it: The ghostly blue flickering of Shrek or some such in the back of an SUV (apparently, children are no longer able to amuse themselves with books, license-plate bingo, or looking out the window). Do they pose a risk for the general traffic stream?

According to a paper by Julie Hatfield and Timothy Chamberlain of the NSW Injury Risk Management Research Centre in Australia, “The impact of in-car displays on drivers in neighbouring cars: Survey and driving simulator experiment,” published in Transportation Research Part F: Traffic Psychology and Behaviour, there is reason to think those displays do effect the behavior of other drivers. Using a driving simulator (this is one of those experiments that would be almost impossible to carry out in actual traffic) with a nearby laptop to simulate in-car displays, the researchers had subjects carry out a number of drives in which they were instructed both to look for the displays, and to ignore them, and drives in which no instructions at all were given (curiously, the effects were similar in this case to when drivers were told to look for the screens). A number of differences were observed in drives in which the displays were present versus when they were not, including a more variable lane position and a slower response time to pedestrians.

What the study seems to suggest is that we can’t but help pay a bit of attention to those moving images in other vehicles. This may depend, of course, on the traffic conditions in the moment; i.e., if we were busy attending to many other stimuli in the environment we would likely screen out non-essential things. But there is that notion too that there’s something inherently seductive in the moving image (as the hypnotized children in the back row will attest to), and that may engage us, almost against our will. The researchers note that their use of a laptop screen does not purely replicate the small screens seen at a distance in the back of cars; but then again, those may cause even more trouble. As they write: “Once attention has been attracted, the smaller screens may produce greater impairment because of the greater cognitive capacity required to make out the materials being screened. Thus, if anything, our results may underestimate the impairment produced by attending to the smaller audiovisual display units that are currently available in vehicles.”

In-car backseat screens are an example of how technology is added to cars for reasons of marketing without really knowing how it will change the driving environment — and, as I mentioned earlier, it is vastly challenging to test such things. I am not suggesting that these have caused a raft of crashes or anything, but given the inaccuracies of crash reporting and the complex interplay of variables present in traffic, it’s actually fairly hard to tell what the effect of the screens is. Perhaps the overall calming effect they have on the passengers in the vehicles in which they are present — and thus the reduction of distraction on those drivers — is more beneficial than the distraction effects they pose to other drivers. In essence, though, they seem to fall into one of those regulatory black holes, in which they are permitted because there’s no evidence they are causing harm, even if that evidence would be incredibly difficult to acquire.

David Williams of the Telegraph gives a prototype vehicle equipped with Intelligent Speed Adaptation (what used to be known as a “governor”) a spin through London. The car limits speed to whatever the limit is on the segment — typically 30 mph.

This line struck me:

Like most motorists I want to be law-abiding. Up until now I’d believed I was. But this clever car exposes such self-delusions. Normally I try to keep to 30mph in town but in reality I must have been doing nearer 40 as I never drive this slowly.

Someone recently asked me, “why do people speed?” There’s no short answer to that question (I’ve got 250-page reports tackling the question), but one possibility that must be considered, in light of the above sentences, is that: They actually don’t know how fast they are going. Any number of studies have shown how drivers, particularly when the feedback is noisy — i.e., they’re sitting high up from the road, the car cabin is ultra quiet (or the radio loud), the road is very wide — routinely underestimate their speed.

As we’ve banged on here about many times before, these minor differences in urban speed, while inconsequential and almost imperceptible for the driver, can be of dramatic importance for the pedestrian or cyclist struck by a vehicle.