How long-haul motor carriers determine truck driver work schedules: The role of shipper demands

Tight delivery schedules have been blamed for widespread violations of hour s-of-service rules by interstate tractor-trailer drivers. The purpose of th e present study was to identify determinants of drivers' schedules, particu larly delivery requirements of shippers. Long-haul drivers were surveyed at weigh stations in Wyoming and Tennessee and asked who had arranged their c urrent loads. The arranger, usually a motor-carrier dispatcher, then was in terviewed by telephone. Interviews were conducted with 270 of 309 identifie d dispatchers. Revenue was the most frequently cited factor (75%) in decisi ons to accept or reject loads fr om shippers. Delivery deadlines (24%) and the hours-of-service status of the nearest driver (9%) were cited much less . Dispatchers reported that shippers ask for sufficient time for drivers to adhere to both speed limits and hours-of-service rules. Trip mileage is re ported as the key determinant of trip schedule assignments (58%); however, other factors also are considered, including speed limits (27%) and past ex perience with particular routes (13%). About two-thirds of the dispatchers reported using rule-of-thumb average travel speeds. Overall, 14% of dispatc hers reported that they expected drivers to travel at an average speed in e xcess of 60 mph. Tight delivery schedules and hours-of-service violations c an occur if rule-of-thumb average speeds above 60 mph are the primary basis for assigned trip times. This survey suggests that tight schedules cannot be attributed solely to shipper demands. (C) 1999 National Safety Council a nd Elsevier Science Ltd.