study indicates greater fuel efficiency at higher speeds than earlier studies; for example, some vehicles achieve better fuel economy at rather than at , although not their best economy, such as the 1994 Oldsmobile Cutlass Ciera with the LN2 2.2L engine, which has its best economy at (), and gets better economy at than at ( vs ). The proportion of driving on high speed roadways varies from 4% in Ireland to 41% in the Netherlands. When the US National Maximum Speed Law's speed limit was mandated from 1974 to 1995, there were complaints that fuel economy could decrease instead of increase. The 1997 Toyota Celica got better fuel-efficiency at than it did at ( vs ), although even better at than at ( vs ), and its best economy () at only . Other vehicles tested had from 1.4 to 20.2% better fuel-efficiency at vs. . Their best economy was reached at speeds of (see graph). Officials hoped that the limit, combined with a ban on ornamental lighting, no gasoline sales on Sunday, and a 15% cut in gasoline production, would reduce total gasoline consumption by 200,000 barrels a day, representing a 2.2% drop from annualized 1973 gasoline consumption levels. This was partly based on a belief that cars achieve maximum efficiency between 40 and 50 mph (65 and 80 km/h) and that trucks and buses were most efficient at . In 1998, the U.S. Transportation Research Board footnoted an estimate that the 1974 National Maximum Speed Limit (NMSL) reduced fuel consumption by 0.2 to 1.0 percent. Rural interstates, the roads most visibly affected by the NMSL, accounted for 9.5% of the U.S' vehicle-miles-traveled in 1973, but such free-flowing roads typically provide more fuel-efficient travel than conventional roads. Differences in testing standards Identical vehicles can have varying fuel consumption figures listed depending upon the testing methods of the jurisdiction. Lexus IS 250 – petrol 2.5 L 4GR-FSE V6, 204 hp (153 kW), 6 speed automatic, rear wheel drive Australia (L/100 km) – 'combined' 9.1, 'urban' 12.7, 'extra-urban' 7.0 Canada (L/100 km) – 'combined' 9.6, 'city' 11.1, 'highway' 7.8 European Union (L/100 km) – 'combined' 8.9, 'urban' 12.5, 'extra-urban' 6.9 United States (L/100 km) – 'combined' 9.8, 'city' 11.2, 'highway' 8.1 Energy considerations Since the total force opposing the vehicle's motion (at constant speed) multiplied by the distance through which the vehicle travels represents the work that the vehicle's engine