Absence of conflict of interest.
The study's objective was to examine the impact of hiring experienced drivers and paying them higher wages, rather than hiring new drivers and paying lower wages, on continued employment at the company and the likelihood of getting into a crash.
The authors used a statistical model to compare the probability of continuing to work for the company and of crashing in a given month for drivers in the lower experience, lower pay group versus the higher experience, higher pay group. The data source is employment records from the freight transportation company, J.B. Hunt.
The study reported no statistically significant relationship between driver experience and ongoing employment or the risk of crashing.
This study receives a low evidence rating. This means we are not confident that the estimated effects are attributable to paying higher wages for more experience; other factors are likely to have contributed.
Higher Base Wages and Experience-based Raises for Drivers
Features of the Intervention
The freight transportation company J.B. Hunt changed its approach to hire experienced drivers and pay more per mile driven, rather than hiring student drivers, training them, and paying low rates per mile. As part of this organizational shift, supervisors also paid more attention to safety issues and recognized driver concerns, truck maintenance was performed more frequently, drivers with poor safety records were terminated, benefits packages were enhanced, and drivers were guaranteed returns to their home terminals within 14 days.
Features of the Study
The authors used a statistical model to compare the outcomes of treatment and comparison group members, comparing how many months drivers stayed at the firm (remained employed) and their probability of crashing each month, controlling for background factors like the drivers’ demographics and operational factors like the number of miles driven. The treatment condition is drivers who were already experienced when hired by the firm and were paid a higher rate per mile driven (0.58-0.60 cents per mile in 2018 dollars). The treatment period was the 13 months from February 1, 1997, to February 28, 1998. The comparison condition is drivers who were originally hired by the firm as students without prior trucking experience, were trained by the company, and were paid a lower rate per mile driven (0.37-0.40 cents per mile in 2018 dollars). The comparison period was the 13 months from September 1, 1995, to September 30, 1996. The study includes 11,457 unique drivers (87,887 driver months). In the full sample, about 96% of drivers were male and 77% were White. The mean age at the start of the study was 40 years old, with a range from 20 to 76 years old.
- The study reported no statistically significant relationship between driver experience and ongoing employment.
Health and Safety
- The study reported no statistically significant relationship between driver experience and chance of crashing.
Considerations for Interpreting the Findings
The treatment and comparison groups were hired at different points in time. The 13 months of observation for those in the treatment group began in February 1997, while the 13 months of observation for those in the comparison group began in September 1995. Therefore, the study cannot disentangle any effects that might be due to the intervention from those that might be due to other changes that occurred at the same time.
Causal Evidence Rating
This study receives a low evidence rating because the groups being compared are from different time periods. This means we are not confident that the estimated effects are attributable to paying higher wages for more experienced drivers; other factors are likely to have contributed.