Based on a price of $3.75 for gasoline, a 15 mpg vehicle will incur a cost of 25 cents per mile, while a 30mpg vehicle will incur a cost of 12 cents per mile.
The trouble is that that $3.75 includes taxes that are supposed to cover road maintenance. And sooner or later those taxes will have to be replaced by something else, likely paid when you renew your license plates and likely designed to be more expensive for cars that use less/no gas.
I think the portion of gasoline tax for road maintenance amounts to less than a cent per mile, while the frequently quoted cost for road maintenance is 5-6c per mile per car. Thus it is already being funded from other sources.
The thing to do in the pitch is to demonstrate that you understand the problem space thoroughly, i.e. rather than pitching the solution, pitch yourselves as the best people to discover and implement the solution.
I too have worked at a company that learnt this the hard way.
There doesn't seem to be a stylish looking electric on the market yet. Something that might change once BMW release the i3.