Something I haven't seen mentioned is yearly adjustments to dollar amounts allowed. A policy that was generous for traveling sales guys 7 years ago doesn't equate to generous in today's economy. Two companies I've worked for haven't changed anything in that length of time. At least for me, the same cities I've covered for more than a decade have seen much higher airfare, hotel, and to a lesser extent food cost.

Also, be open to overall trip cost. I live between COS and DEN, but driving to DEN is often on the tollway (E-470), much higher parking cost, not to mention employer is paying me miles on my personal vehicle. If it's overall cheaper for me to fly out of COS, despite the higher ticket cost, there needs to be some logic in that. I will punch the next accountant that would prefer that I never violate a policy in order to save the company money for the entire trip... Usually small companies, and once the CEO finds out I actually care and think big picture, it's fine after that, but what a pain to deal with some bean counter that hasn't a clue what they are doing.