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 hours-of-service rules by interstate tractor-trailer drivers. The purpose of the present study was to identify determinants of drivers' schedules, particularly delivery requirements of shippers. Long-haul drivers were surveyed at weigh stations in Wyoming and Tennessee and asked who had arranged their current loads. The arranger, usually a motor-carrier dispatcher, then was interviewed by telephone. Interviews were conducted with 270 of 309 identified dispatchers. Revenue was the most frequently cited factor (75%) in decisions to accept or reject loads from 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 reported as the key determinant of trip schedule assignments (58%); however, other factors also are considered, including speed limits (27%) and past experience with particular routes (13%). About two-thirds of the dispatchers reported using rule-of-thumb average travel speeds. Overall, 14% of dispatchers reported that they expected drivers to travel at an average speed in excess of 60 mph. Tight delivery schedules and hours-of-service violations can 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.