On July 15, 1997, at 0445 mountain daylight time, a Piper PA-31-350, N800SA, operated by American Check Transport, Inc., d.b.a. as Flight Line 101, collided with an airport employee shuttle bus during taxi from landing, at Denver International Airport, Denver, Colorado. The aircraft sustained substantial damage and the airline transport certificated pilot, who was the sole occupant aboard the aircraft, was not injured nor were the three persons aboard the bus. The bus also sustained substantial damage. Visual meteorological conditions prevailed for this Title 14 CFR Part 91 positioning flight which originated at Arapahoe County Airport, Englewood, Colorado, approximately 15 minutes prior to the accident. According to information provided by Denver International Airport Operations, the aircraft was taxiing in a non movement area under ramp control and was proceeding to the cargo area following landing, and the bus failed to yield the right of way at an airport road/ramp taxiway crossing. The left wing of the aircraft came in contact with the right front window and right windscreen of the bus. The outer portion of the left wing on the aircraft was sheared off and the right windscreen, right side window, and right front support structure on the bus were broken. (See attached photographs). According to the pilot, as he was taxiing down taxiway SC a bus pulled out in front of him from the vehicle service road which crosses the taxiway. He said he tried to turn but was unable to avoid having the left outer wing contact the bus. The pilot said his position and beacon lights were on. Bus driver and bus passenger statements taken by airport operations persons provided information that the driver and passengers did not think the aircraft lights were on. The statements also provided information that a clear Plexiglas partition on the right side of the bus interior caused limited visibility from the right side of the bus. As a result of this finding, the airport operations department instructed the bus company to remove the partition from all buses operating on the airport. Examination of the aircraft by an FAA inspector provided information that he found the position light circuit breaker popped. He said he could not determine if the breaker position was the result of shorts which could have occurred during the accident. Investigation revealed that ramp control is not an air traffic control function and is operated by the airport as an advisory service for non movement areas. Also, the portion of taxiway SC where the accident occurred is lighted only by standard taxiway lights and the background is a standard parallel taxiway. At the time of the accident, a large aircraft with taxi lights on was proceeding south on taxiway 'M', behind and to the north of the accident aircraft. This should have illuminated the accident aircraft Denver International Airport has a training program which provides class room instruction, practical instruction, testing, and monitoring of all persons permitted to drive on the airport. A review of the program provided no indication that it is deficient., and the bus driver had been through the program with no deficiencies noted.