Roads have been designed as wide, straight routes, with few obstructions to the motorist's vision or progress, and strict barriers or space between vehicles and pedestrians. Traffic calming, by contrast, seeks to do the opposite. The goal is to slow vehicular traffic, and in some cases discourage drivers from using certain roads. By altering the design of the road, introducing obstacles, and otherwise making the path a bit more difficult for vehicles, motorists will be forced to drive more slowly and carefully. There are dozens of techniques for this, ranging from narrowing the roadway, to creating medians, to allowing on-street parking, to installing speed humps.
Many proponents believe it also reduces accidents, though that claim is less well documented.
Police, fire and ambulance response times will be slowed. Some designs bring pedestrians, parked vehicles and bicyclists in closer proximity to moving cars, which may increase safety risks. Slower vehicle traffic could create traffic back-ups. Not all drivers will navigate the obstacles designed to slow their speed. Roadway alterations require construction costs.