Use Your Illusion II: Virtual Speed Humps Coming to Philly


Desperate times call for desperate measures. As part of a city-wide campaign to reduce speeding, Philadelphia is marking 100 intersections with painted-on faux speed humps, like the ones pictured above. Britain’s Telegraph reports:

"The goal is to change the mindset," said Philadelphia’s chief traffic engineer Charles Denny.

"The driver sees this in the roadway, and they think that it’s some protrusion up out of the roadway, and not a perfectly flat surface. So they slow down before they drive over it."

Accident data will be collected by the National Highway Traffic Safety Administration to see if the pioneering scheme actually does make the roads safer.

The virtual humps are the latest innovative measure adopted as an alternative to traditional "sleeping policemen", which have been criticised for damaging cars, slowing down emergency vehicles, and lowering fuel economy.

We admire the Engwichtian spirit here, but it’s not immediately clear how much of an impact virtual speed humps will have on drivers who, for example, pass over them more than once. And they don’t sound nearly as much fun as the laser crosswalk wall, or this one:

Rubber speed humps that inflate only when a speeding vehicle approaches have been successfully tested in London.

Streetsbloggers, what say you? 

Photo: Telegraph

  • As long as I don’t get mistaken for a virtual pedestrian.

  • Matt Kime

    I think they’ll work once or twice then people will catch on to them – particularly people following a frequently used route.

  • I agree with Matt above. I’d even say that if they all look the same, driving over one ANYWHERE will pretty much give the game away and drivers will ignore all of them. Maybe if they mix in some real ones that look identical to the fake ones, drivers won’t know which they’re approaching?

    What’s really needed are some kind of retractable speed bumps that can be de-activated by special vehicle-mounted transponders (I’m thinking of the ones they’re already using to change lights for buses and emergency vehicles).

  • paul

    Nice GnR reference. who knew that streetsblog brass are metalheads?

    Seriously though, i see these having much diminished effect over time, as motorists get hip to the ruse. properly built speed humps or speed cushions (which can be spaced to allow emergency vehicles to pass) work fine. add neckdowns speed cams to enforce a lower speed limit (20 mph anyone?) and you have a much more effective calming strategy. its more expensive, but worth it because crashes are even costlier.

  • Well, we’re all agreeing on this. Clearly it’s a questionable if not bad idea and there are other things that work… like bollards making roads a tight fit for cars will slow down the speed or alternate the sides on which you have them to make it a little more windy, etc.

  • Boots

    Narrow the street, put parking along both sides. Narrow streets equals slower speeds as people don’t want to hit parked cars or people (one would hope).

    The equation for “How narrow?” is easy. A standard car is 8 feet wide, (excepting smart cars and hummers, but average) so then each lane should be dealt with accordingly.

    A standard parking lane then is 8-9 feet, and a driving lane of moderate speed is 10 feet. Increasing the driving lane size, say to 12 or even 14 feet makes for a very fast street. To make a SLOW street narrow the lane to 9 or even 8 feet.


    Slowish street: (2)Parking lanes 9ft each + (2) driving lanes 9 ft each = 36ft.

    Slowish street: (1)Parking lane 9ft each + (1) driving lane 9 ft each = 18ft.

    VERY SLOW street: (2)Parking lanes 8ft each + (2) driving lanes 8 ft each = 32ft.

    EVEN SLOWER STREET: (2)Parking lanes 8 ft each + (2) driving lanes with pullouts at 14 feet = 30 ft.

    You get the point and the math to make other streets works the same. Wide streets = fast streets, narrow streets = slow streets. The corrolary is that slow streets are SAFE streets for pedestrians.

  • anon

    i’d support this if it was done by intrepid volunteers, a la roadsworth. but an official agency has the resources to do something more effective.

  • mr. brownstone

    Boots – thoughtful comment – but one change: standard parking lanes in NYC are 8′ or, on streets with little to no trucks parking, 7′. On bus routes it’s sometimes more.

  • It seems like a terrible idea to use optical illusions of any kind where driving is concerned. What’s wrong with real speed bumps, roundabouts, and other physical barriers?

    Creating an environment where something isn’t as it seems and drivers don’t experience the actual bump they expect could easily lead to drivers ignoring real speed bumps and having accidents as a result.

    Let’s ‘keep it real’.

  • I don’t know, I actually think it might work. I have a feeling people have an auto response to seeing something in the road, which will kick in even if they’ve been on the route over and over. i guess only time and data will tell.

    (Which is not to say that municipalities shouldn’t be doing all the things suggested above — they should — just that this might be a fairly cheap and effective way to achieve some speed reductions.)

  • Brooklyn Boy

    I wonder if it would be admissable in court (for whatever reason), and then use that as an excuse for a red light ticket claiming to have considered it an optical illusion etc. LOL.

  • galvo

    the speed limit needs to be lowered to 20 mph in these congested urban areas.

    i remember the gas crisis of the 70’s. The federal govt mandated that all highways had to reduce the speed limit to 55 mph to conserve fuel. Latter when the fuel crisis was over they tried to retain the speed limit at 55 mph to save lives.

  • I can’t honestly say whether or not I dig this. I open my mouth and nothing comes out. Seriously. Equal parts clever and a head scratcher – even my fingers are having a hard time typing this…..
    Okay, I give up. Maybe tomorrow I will have an opinion.

  • djsbon

    i think it’s a great idea and i can’t wait to see them in philly ūüôā

  • what the?

    Um, that looks like something that could damage a car. Hope no one swerves and causes a crash.

  • Would anyone like to report firsthand on the results of this experiment with virtual speed bumps in Philadelphia?¬† Does anyone know if the accident data collected by the National Highway Traffic Safety Administration is available online?¬†

  • Would anyone like to report firsthand on the results of this experiment with virtual speed bumps in Philadelphia?¬† Does anyone know if the accident data collected by the National Highway Traffic Safety Administration is available online?¬†

  • Adamchan0602

    Make them look like real speed bumps and have real speed bumps in some areas, should help keep people honest.


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