Heh... I heard an expression a while back that stuck with me: "everyone's a lawyer and everyone's a traffic engineer."
Robert Roaldi wrote on 03/09/11 at 07:55:13:I wonder if anyone has statistics on accidents during power black-outs. That's almost like eliminating traffic lights, and might be a good proxy for conducting a more thorough experiment.
I don't have any firm data, but I have some anecdotal evidence of collision rates sharply increasing during blackouts.
However, it's not a good comparison:
- even with signals, it looks like the street in the video was fairly low-speed and low-volume: the video talked about 2000 vehicles per hour (apparently for the intersection, though the video wasn't clear on what it was referring to); a busy urban intersection in Southern Ontario will experience many times that volume, and be carrying traffic at much higher speeds.
- I looked at the the area where the signals were removed in Google Maps: most of it is a jumble of narrow streets, sharp intersection angles, and weird multi-leg and offset intersections... all the normal hallmarks of a town core that was laid out before the age of the car. In general, this is a particularily difficult sort of area to signalize anyhow. North American-style wide streets on a grid arrangement were (usually) designed with signalization in mind and can normally handle being signalized much more efficiently.
- kinda building on that point, it's not like they council in the video would've just decided to get rid of signals without any sort of review or analysis to see what happened. It's likely this decision was the result of lots of traffic operations analysis, safety analysis, and probably a fair bit of simulation. It's also quite possible that if this review had found that this location
wasn't a good candidate for removal of signals, they would've shelved the idea and that video would never have been made. There are a lot of tools in the traffic engineering toolbox, and no one tool is appropriate for all situations.
- a big factor affecting safety is driver familiarity and expectation. It's one thing to decide to remove signals from an intersection
after a huge public notification campaign so the residents know what to expect. It's a whole different thing to just "flip the switch" and turn the lights off without warning.
Disclaimer: while I am a traffic engineer, this post is not meant as formal engineering advice or an official opinion. It should not be relied upon for any matter.