Several types of guideways have been proposed or implemented including beams similar to monorails, bridge-like trusses supporting internal tracks, and cables embedded in a roadway. Most designs put the vehicle on top of the track, which reduces visual intrusion and cost as well as easing ground-level installation. An overhead track is necessarily higher, but may also be narrower. Most designs use the guideway to distribute power and data communications, including to the vehicles. The Morgantown PRT failed its cost targets because of its steam-heated track, so most proposals plan to resist snow and ice in ways that should be less expensive. Masdar's system has been limited because it attempted to dedicate ground-level to PRT guideways. This led to unrealistically expensive buildings and roads.