FACTBOX: Some facts about U.S. gas taxes

(Reuters) - U.S. Republican presidential hopeful John McCain proposed a summer gas tax reduction and other tax cuts on Tuesday. Following are some facts about U.S. gas taxes:

* Fuel tax receipts fill a trust account that helps underwrite U.S. road and transit projects. Suspending it for three months would eliminate $7 billion for highway construction and $2 billion for rapid transit, industry estimates.

* Transportation advocates said a gas tax reduction may save motorists money at the pump, but unless the difference is made up elsewhere the reduction would cut jobs and payroll tax receipts as well as affect construction, equipment and materials companies.

* The gas tax has remained at 18.4 cents per gallon since rising more than 4 cents in the early 1990s.

* Some in Congress have advocated a gas tax increase to help close a shortfall in money for infrastructure projects. Others have called for an increase to spur greater fuel conservation.

* Road projects are popular federal budget earmarks, or pet projects, coveted by lawmakers because they create jobs and other economic benefits for their states or districts.

McCain has railed against such "pork barrel" spending for years.

(Reporting by John Crawley in Washington; editing by David Wiessler)