"Many fires occur while buildings are under construction, which may be the time structures are the most vulnerable. In order to provide fire suppression forces prompt and efficient access to a job site, the fire codes require fire apparatus access roads that are capable of supporting heavy fire equipment. Construction site access road specifications differ in the two major model codes. The International Fire Code® requires 'approved' vehicle access and specifies that the road must extend to within 100 feet of temporary or permanent fire department connections. Permanent access roads must reach within 150 feet of all portions of the exterior wall of a building's first floor."
Coffee Break Training - Fire Protection Series No. CB-2005-4
United States Fire Administration: http://www.usfa.fema.gov/