ddna talk - options

Traffic calming options

Several options are available as traffic-calming measures. Besides naturally slowing down traffic, they generally also beautify the streets on which they are applied.
  • Narrow the street
    Streets are usually designed to maximize traffic flow, and roadbeds are typically wider than they need to be if the design goal is merely to allow access. Narrowing streets to the minimum reasonable widths is quite effective in slowing cars down. To set the scale, the width of Buena Vista at the intersection with Galisteo is 18'. In the city's 'Urban Design Guidelines', a street whose function is 'residential neighborhood access', has a curb-to-curb distance of 16'.

  • Introduce curves
    If there is enough space, a straight street can be turned into a winding trajectory, typically in conjunction with plantings and parking spaces in strategic spots.

  • Changes of pavement
    Changes in the road surface, even without height changes, tend to cause cars to slow down, especially if the new surface look like they might be pedestrian territory. Blacktop, cobbles (real or stamped), colored concrete and brick are options.
    Another place where changes in pavement can be used is in the way parking spaces are implemented. Normally, when a street has curbside parking, blacktop (or concrete), is laid smoothly from curb to curb. This means that when there are no cars parked, the width available to cars is almost twice as wide as when there are cars parked on both sides. What you can do instead, is to have the actual road surface be blacktop, and the parking spaces made out of a different material, such as cobbles (a bumpy surface is ok for parking, but not for driving), or concrete.

  • Plantings
    If the curb merely is a boundary between the blacktop and wide-open dirt or concrete, the street will seem wider (to motorists) than if there is something placer right along the curb. This includes plant boxes, railroad-tie raised beds, or shrubbery without boxes.
    Rows of trees along one or both sides of the street also make the street visually smaller, resulting in lower speeds.

  • Bumps, humps and dips
    Speed bumps are effective, but not well-loved by the public. They are also not friendly to city buses. This last problem can be solved by making the bumps only as wide as the space between the buses wheels, so they can straddle the bump. Cars however have a narrower wheelbase, and therefore cannot avoid these bumps. Dips are as effective as bumps, and they can double (or pretend to double) as drainage channels.
    Humps are gentle rises, followed by a longish raised section, after which the surface goes down again to the original level. Typically these are combined with changes in surface texture and color.

  • Examples
    • Street widths: Valley drive got narrowed in spots to calm traffic.
      Buena Vista, between Galisteo and Don Gaspar, is 18' on one end and 19' on the other. On-street parking is allowed!
    • Plantings: Valley drive, in the narrowed spots.
    • Surface changes: In Los Alamos, in front of the post office and library, the trick with the different parking space surface is nicely implemented.
      In White Rock, the red-cocnrete stamped cobbles are used to mark a bicycle path crossing.
    • Bumps: ( there is this neighborhood off Rodeo Road )

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Last update: 6 May 97 - Hubert van Hecke