Reduce local travel costs by creating financial incentives to use public transit in lieu of taxis and rental cars.
Possible incentives could include:
1) Permit travelers who choose public transit over more expensive transit to keep 1/3 of the savings.
For example, if a traveler spends $4.50 to get to/from O'Hare airport to downtown Chicago using public transit, in lieu of spending $80 on taxis for the same trip, allow the traveler to keep approximately $25 of the $75.50 in savings. The government would save approximately $50.
2) Create an optional "local transit" per diem for each locality for which GSA computes per diems, keyed to the cost of public transit within that locality, where available. For example in Washington, D.C., suppose such a per diem were set to $15 per day. A traveler visiting her agency's headquarters for two days, who might otherwise take several taxi rides or rent a car for two days, at a cost of upwards of $80, might instead opt to purchase two one-day unlimited passes for the Metro rail system, for approximately $18. The traveler would keep $12 in unused per diems ($15 x 2 days - $18), and the government would pay approximately $50 less. Travelers would have the option of choosing the local transit per diem (and foregoing reimbursements for taxis, etc.) or choosing to use the current option of reimbursment for all transportation costs.
In connection with this, it would be useful to compile information about (or links to information about) public transit options in various cities on a single webpage on GSA's website.
This would save the government money and benefit the environment, while expanding options for federal travelers.