Currently, I know of no requirement or incentive for employees on travel status to conserve government resources by taking the cheapest form of travel possible once they have arrived at their destination city -- i.e., taking metro to get from the airport to the hotel versus taking a taxi. Giving employees an incentive to conserve government resources -- frequently at somewhat of an inconvenience to them -- would allow for greater savings of government money. Perhaps travelers choosing the cheaper, less convenient travel mode could be entitled to 25-50% of the savings that result -- if the cab ride was $10 more expensive than the metro fare, the employee choosing to ride metro would get an extra $2.50-$5.00. Additionally, the cheaper option is frequently the "greener" option, also resulting in a more environmental choice that should also be rewarded.
Idea No. 7573