?_Giannini: a question about non owned auto liability

We have had very few choices in insuring this risk for the past few years. A local insurance agency called to inform me he had a company who did pizza restaurants with delivery …so we set up a meeting. The non-owned auto liability premium is based on actual drivers payroll and is set at $8.75/$100 of drivers payroll. This seems to be a very poor way to estimate risk to me…as the actual number of deliveries is available for anyone who might want to check. But, if this is how this particular agency calculates it’s premium, I’m wondering just what exactly is drivers payroll? Given that my employees do every job an establishment needs to survive (plus deliver), this is a rural area where on slow nights an employee can work 4 hours with only 6 or so deliveries…am I allowed to to estimate how much time my delivery people actually spend in their cars? Just wanted to bounce this off you before my next meeting. Thanks for any help