as to what would have been a reasonable speed, the driver was convicted. The driver appealed to the Montana Supreme Court. The Court reversed the conviction in case No. 97–486 on December 23, 1998; it held that a law requiring drivers to drive at a non-numerical "reasonable and proper" speed "is so vague that it violates the Due Process Clause ... of the Montana Constitution". Effective May 28, 1999, as a result of that decision, the Montana Legislature established a speed limit of . Montana's US, State, and even Secondary roads have speed limits posted 70 mph/night:65; truck:60/night:55. Seven years later, a research study conducted by the Insurance Institute for Highway Safety, a long-time advocate of the federal National Maximum Speed Law, showed Montana's 75 mph speed limit on rural Interstates was well received by motorists; traffic speed measurements taken by IIHS showed 76 percent of cars in compliance with 75 mph on those roads. IIHS also found large trucks subject to Montana's unchanged 65 mph speed limit for large trucks on rural Interstates slowed down dramatically, from a mean speed of 70 mph in 1996 to 65 mph in 2006, with the 85th percentile large truck speed dropping 11 mph, from 79 mph in 1996 to 68 mph in 2006. 75 and 80 mph speed limits Despite this reversal, Montana's then-governor, Marc Racicot, did not convene an emergency session of the legislature. Montana technically had no speed limit whatsoever until June 1999, after the Montana legislature met in regular session and enacted a new law. The law's practical effect was to require numeric speed limits on all roads and disallow any speed limit higher than . Montana law still contains a section that says "a person shall operate a vehicle in a careful and prudent manner and at a reduced rate of speed no greater than is reasonable and prudent under the conditions existing at the point of operation, taking into account the amount and character of traffic, visibility, weather, and roadway conditions." However, this is a standard clause that appears in other state traffic codes and has the practical effect of requiring a speed lower than the speed limit where a lower speed is necessary to maintain a reasonable and prudent road manner. Montana also has limited sections of night speed limits. Other speed limits in Montana are in a school zone, in a residential district, on boulevards,