The research, which polled more than 42,000 managers working in the transport industry, including more than 1,200 fleet managers, shows there is a £6,207 difference in overall take home pay among female and male managers in the sector.
The findings by the Chartered Management Institute (CMI) and Remuneration Economics also show resignation rates for women stand at 2.6% – up from 2% last year.
Only 2.6% of women said they were inclined to ask for internal transfers if they are dissatisfied with their current role, compared to 3.7% of men.
Jo Causon, director, marketing and corporate affairs at the CMI, said: “It is clear the pull of promotion is not being matched by parity in pay.
“Despite the weight of legislation and the reality that reward should match responsibility, gender bias seems to be getting worse, not better.”