blowers are usually ineffective at clearing ice. Picks are sometimes used, but a solid spade can break through most ice. There is always the risk of damaging the pavement with these instruments. Icy areas can be covered with salt or some other substance, bags of which are widely available. A recent technological advance is the snowmelt system that heats the pavement from below and melts snow and ice after a period of time. Such systems are expensive to install and operate and they are not cost effective in areas with very low winter temperatures and large snowfalls. Some governments offer free snow clearing for the elderly and others in need. In some cities, snow clearing for elder and handicapped residents counts towards community service hours assigned as a punishment for minor offences. In some places, laws require homeowners to clear snow from the public sidewalk in front of their house, as well as a pathway on their own property to their mailbox. Those who fail to do so, depending on the jurisdiction's laws, may experience fines and may be civilly liable for injuries suffered by another on a surface that they were required to clear. In some jurisdictions, such as New York, private home owners who shovel are held civilly liable for others' injuries incurred by falling in areas that have been shovelled. Cleaning off and freeing one's vehicle is another matter. Some people who need their vehicles will only do barely what is necessary in order to drive the vehicle and remove it from its space. Failure to clear all the snow and ice from a vehicle causes hazards by impairing the driver's visibility, and ice from the roofs of driven vehicles can cause crashes. In some jurisdictions, motorists who fail to clear snow from their vehicle entirely may be fined. Others may be more thorough in this process. In some urban residential areas with curbside parking, residents use objects to mark the spaces they dug out so they can reclaim their space upon their return. A leaf blower is sometimes used to blow light powder snow from vehicles, driveways, walkways, and decks. This only works well for very light powder snow. Clearing by the owners of contiguous lands or buildings In some countries, keeping sidewalks clear and safe in winter is a duty of the owner of the contiguous land or building. The owner can be an individual