plowing methods or blown to an area of the property by snowblowers. Contractors may apply sand or salt in some locations to help melt ice accumulations. Many snow removal contractors will require installation of snow poles or snow staking along the driveway. This is to keep equipment out of the landscaping and to help identify the perimeter of an area. Clearing by municipalities Cities clear snow on a much larger scale than individuals. Most cities in areas that get regular snowfall maintain a fleet of snow clearing vehicles. The first to be dispatched are gritters who do some plowing but also salt the road. The salt, via freezing point depression, helps melt the snow and ice and also gives vehicles more traction. Later, usually when the snow has ceased falling, snow plows, front end loaders with snowplow attachments, and graders cover every street pushing snow to the side of the road. Salt trucks often then return to deal with any remaining ice and snow. The trucks generally travel much faster than the plows, averaging between 30 and 40 kilometers per hour. Most cities thus have at least twice as many plows as trucks. Smaller narrow body plows, with Caterpillar tracks or huge snow tires salt and clear sidewalks in some cities, but in many others with less snowfall and/or less pedestrian traffic individuals are tasked with clearing the sidewalk in front of their homes. Ecological movements often oppose this use of salt because of the damage it does when it eventually washes off the roads and spreads to the environment in general. Credit for the concept that municipalities should remove snow from public roadways usually goes to Edward N. Hines, a celebrated early 20th century transportation thinker who also was the first to put a painted center line stripe on an automobile-era road. In cities where snow steadily accumulates over the winter it is also necessary to remove the piles of snow that build up on the side of the roads known as windrows or snowbanks. There are a number of methods of doing this. Pulling snow is done when temperatures rise high enough for traffic to melt snow. The windrows are then broken up and spread over the road. Casting is the moving of snow by means of a shovel or plow to nearby public lands. On boulevards or highways winging back is done, which consists of pushing the