WEIGHT ENFORCEMENT AND EVASION: OREGON CASE STUDY

This study examines the incidence of overweight trucks and its relation to regulatory enforcement activity. Addressed are questions of scale operations in relation to weight violations and the effectiveness of enforcement levels, automated preclearance systems and weigh-in-motion (WIM) technology. The study also compares state-by-state enforcement intensity and penalty levels to understand their relative effective deterrence. To answer these questions the Oregon Department of Transportation (ODOT) identified an i-5 freight corridor and two potential bypass routes to collect data from three WIM sites. Data collection occurred before, during and after an extended closure of the I-5 weigh station. The traffic volume data did not indicate evasion behavior on the bypass routes, nor diversion to I-5 during closure. Only the I-5 site exhibited a statistically significant pattern of increase in mean GVW from baseline through closure (.4%) and a decrease of 1.2% following reopening. The incidence of overweight vehicles on I-5 also exhibited a statistically significant increase from 2.27% before closure to 3.67% during closure and a decline to 3.19% after re-opening. Additional analysis explored the incidence of overloading among ODOT Green Light preclearance program participants. Green Light program participants were less responsive to scale closure than non-participant vehicles. The study results suggest the following: 1) Relatively aggressive enforcement in Oregon (more weighings and stiffer fines for overweight violations) creates a climate where a single-site temporary suspension of weighing activity has less impact on trucking operations; 2) Weight enforcement activity at one site on I-5, the major West Coast freight corridor, may have little impact on interstate and international shipments; and 3) Green Light program participants may be either self-selecting compliant operators or, unwilling to jeopardize the benefits of the program by engaging in overloading.