According to the American Transportation Research Institute (ATRI), the research arm of the American Trucking Assns. (ATA), preliminary results from an ongoing study of speed governors indicates data is insufficient to make a strong claim about the relationship between fleet size and governor use.

On top of that, there were no statistical relationships between industry segment and use of the speed-limiting devices.

Interestingly, 15% of the respondents that use speed governors said they allowed speed settings to be adjusted, depending on factors like safe driving.

Of those respondents, 64% used it as an incentive to get drivers to follow fleet policies. For example, drivers who met fuel economy and accident avoidance targets would be eligible to have the speed governor setting increased.
www.atri-online.org