Before revision:  Under a wage floor on TNC drivers, we consider two schemes of congestion surcharges : (a) surcharge based on each TNC trip , and (b) surcharge based on each vehicle hour (regardless of whether the vehicle has a passenger or not) .
After revision:  Under a wage floor on TNC drivers, we consider two schemes of congestion surcharges : (a) a charge per TNC trip similar to an excise tax , and (b) surcharge based on each vehicle hour (regardless of whether the vehicle has a passenger or not) .