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These Gentler Speed Bumps Rely On An Optical Illusion To Keep The Roads Safe

by Penn Collins

August 7, 2017

A clever new traffic implementation in Britain has many hopeful that neighborhood streets will be able to to get all the benefits of speed bumps without the jarring disruptions they create. 

With speed bumps, the disruption itself is the deterrent, so the fact that traffic engineers could eliminate the former while maintaining the latter may come as a surprise. But city services have adopted a new “traffic calming” instrument that does just that. 

Simply put, these innovative new tools are nothing more than paint on the ground. However, the paint is applied specifically to create a three-dimensional effect, creating the illusion of a speed bump where there is none. 

Drivers slow down in anticipation of a gentle jolt that never comes. Traffic stays slow, and drivers and their cars don’t have to endure the unpleasant and destructive effects that speed bumps can have. 

This isn’t the first time British road authorities have resorted to altruistic deception to keep streets safe. The city of Cambridge features a “ghost roundabout” that’s proven just noticeable enough that drivers proceed with caution, but not convincing enough that they start to pull into the roundabout, ending up on the sidewalk. 

While a little innovation in the name of safety is never a bad thing, a few exasperated souls have taken to wondering if we really need the terms “lumps,” “bumps,” and “humps.” 

Sadly, it seems we do. A quick breakdown from 99% Invisible explains the differences we may not have known existed between the different traffic control instruments. 

  • Speed bumps: One long stretch of raised asphalt up to five inches tall and a few feet deep, meant to slow traffic to less than ~10 mph
  • Speed humps: One long stretch of raised asphalt up to three inches tall and often deeper than bumps, meant to slow traffic to ~25 mph
  • Speed lumps: Divided humps with the spacing sized to allow emergency vehicles with a wider wheelbase to pass unimpeded
  • Speed tables: Low like humps, but up to ten feet deep and flat on  top, further easing movement while keeping traffic to ~30 mph or less. These sometimes also serve as raised crosswalks.
  • Traffic undulations: Variably defined, but in some cases used to denote sequential sets of speed humps along a longer street. In other cases, the term is used to describe humps or tables.

So while you might not be thrilled that a city is playing with your sense of perspective and optics on the road, remember that the alternative may entail hitting your head and getting your groceries tossed around the car. That should make this new innovation a little more palatable to all involved. 

Share image via Steve D Luddite/Twitter.

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