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From xkcd

3-Way Street from ronconcocacola on Vimeo.

3-Way Street from ronconcocacola on Vimeo.

 Modeled Behavior reports on: Altruism and discrimination in traffic:

"A new working paper by Redzo Mujcic and Paul Frijters uses the question of ‘Who stops for whom in traffic?’ to shed light on several important and interesting issues related to when, why, and for whom we exhibit altruism. Here is how they summarize their results:

We study social preferences in the form of altruism using data on 959 interactions between random commuters at selected traffic intersections in the city of Brisbane, Australia. By observing real decisions of individual commuters on whether to stop (give way) for others, we find evidence of (i) gender discrimination by both men and women, with women discriminating relatively more against the same sex than men, and men discriminating in favour of the opposite sex more than women; (ii) status-seeking and envy, with individuals who drive a more luxury motor vehicle having a 0.18 lower probability of receiving a kind  treatment from others of low status, however this result improves when the decision maker is  also of high status; (iii) strong peer effects, with those commuters accompanied by other  passengers being 25 percent more likely to sacrifice for others; and (iv) an age effect, with  mature-aged people eliciting a higher degree of altruism."

(In Soviet Russia, the Bus Rides You).

From the report, by RTL, "In some Russian cities, shuttle buses are involved in half of all traffic crashes."

I don't know why I didn't see this earlier, World Streets proposes a Street Code

The idea is works is that legal responsibility for any accident on street, sidewalk or public space, is automatically assigned to the heavier faster vehicle. This means that the driver who hits a cyclist has to prove his innocence, as opposed to today where the cyclist must prove the driver's guilt (not always very easy to do).

I suppose there is a conflict if the heavier vehicle is not necessarily faster, or if you get the irrational (drunk) pedestrian or cyclist, but it seems a good heuristic that will give those who impose the greatest unsafety externality the incentive to yield.

Note that all vehicles are expected to yield to trains, because trains can't brake quickly (and they were there before cars in general), despite the fact that trains were heavier.

My favorite five-way intersection (Franklin Avenue/East River Road/27th) has now been signalized for over a month. The video was taken on Oct 11 in the late afternoon (I apologize for the poor angle, but I wanted the same position as before as much as possible, unfortunately the sun did not cooperate (or alternatively the clouds did not obscure the sun), also I reduced the resolution for the Web). Other differences to note are that school is now in session.

The intersection was roughly at capacity (as can be seen), in that most conflicting movements were fully served with approaching cars, though I suspect throughput could be a bit higher.

We observe a throughput of about 1948 vehicles per hour (based on my estimate of 147 vehicles and pedestrians and bicyclists in 4:18), which compares favorable with the more chaotic 5-way stop during reconstruction which served about 1600. There seems a long period of lost time that could perhaps be used to improve capacity/lower delay.

The main difference is the extra capacity due to more systematic parallel movements (yielding more than one critical point). Notice the pedestrians just past the 4 minute mark are still quite confused as to whether to go or not.

As a user, the pedestrian timing is still terrible, and I just go whether or not I have the signal, so long as I am unlikely to be flattened like a pancake by oncoming cars.

From NY Times Smarter Than You Think - Google Cars Drive Themselves, in Traffic : ""

This movie was taken by me, with my iPhone, on the way home from work on August 19, 2010 at 5:22 pm. The five-way stop controlled intersection (Franklin Ave/ East River Road / 27th Ave) seems to have a maximum throughput just over 1600 vehicles per hour. Most of the movements are saturated during the peak. This intersection has been blogged about before.

The downside for a stop controlled intersection is that the allocation of time across legs is "unfair", i.e. drivers are supposed to take turns (yield to the right). Thus a leg which is just saturated will get just as much access to the critical points of the intersection as a leg that is supersaturated, resulting in much higher delays on the supersaturated movements. I did not measure delay, but it is longer on this day for travelers moving WB on Franklin Ave.

There are several other points to note.

(1) Drivers do not all know the "yield to the right" rule.

(2) This results in "negotiations" between drivers about who should go. Less aggressive drivers clearly lose, but eventually go.

(3) This generally increases throughput compared to obeying rules (do not start until the intersection is cleared is violated, to the benefit of throughput).

(4) The intersection is confusing but safe. Any crashes during peak times would be very low speed.

(5) It is more confusing because of the construction.

(6) The intersection was configured with operating signals in September 2010.

More on risk compensation from WaPo Traffic study sees shades of gray in yellow lights summarizes a study from U of Cincinnati

The longer the yellow persists, the more likely it is that drivers will not stop, said Zhixia Li, an engineering PhD student who worked on the study with his professor Heng Wei. In fact, he said, with a long yellow, "stopping is more dangerous," because other drivers are likely to keep going through the yellow, and someone who opts to stop runs a greater risk getting hit from behind.

The WaPo article doesn't actually say this is risk compensation, but drivers familiar with an intersection will be familiar with the length of yellow, and the longer the yellow on average the greater the chance of making it.

Tom Vanderbilt links to an article in Ad Age about the decline in drivers licenses among youth between 1978 and 2008 in the US. This data surprises me, not just the decline in youth licenses, which can be explained as Tom notes by graduated driver's licensing programs, but a decline between 1998 and 2008 for all drivers by age group, which is shown at the bottom of the Ad Age article according to USDOT. While I know auto ownership peaked in the past few years (with a decline in total cars last year), and the recession and high gas prices have changed patterns in the past half decade, this is remarkable if true.

I retain some skepticism about whether this is instead explained by a switch to other forms of IDs among non-drivers, (i.e. in the past a DL was considered standard ID, so people got that from the DMV even if they did not drive) or some sort of other accounting issue.