Newark Liberty International Airport taxi fares carry the highest premium over base fares, according to research from ride-booking service Blacklane that examined fares from the 30 busiest U.S. airports to the nearest major city center. Extras like tolls, peak-hour surcharges, a credit card surcharge and a 15 percent tip add a maximum of $32 to a ride from the New Jersey airport, 53 percent more than the base fare of $60. Across the 30 airports, extra costs totaled an average of 26 percent, according to Blacklane. Other airports at which extras add more than 30 percent to a base fare include Las Vegas McCarran (43 percent); New York LaGuardia (40 percent); Boston Logan (36 percent); Washington, D.C.'s Reagan National Airport (36 percent); New York's John F. Kennedy International Airport (36 percent), Detroit Metropolitan (35 percent) and Fort Lauderdale-Hollywood International Airport (33 percent). Blacklane based its research on data from airports, taxi companies and cost estimator TaxiFareFinder.com.