(also interstate highway) (in the US) a wide road, with at least two lanes in each direction, where traffic can travel fast for long distances across many states. You can only enter and leave interstates at special ramps. compare motorway Culture Interstates have four lanes and run for long distances. They are marked with red and blue signs, an 'I' and the road number. Interstates going east to west have even numbers and those going north to south have odd numbers. I-80 goes from New York to California, and I-95 goes from Maine to Florida. They are usually referred to in this way Cultureroads and road signsThe US road system is the largest in the world, mainly because of the long distances between cities. The distance between Boston and San Francisco, for instance, is more than 3 000 miles/ 4 827 kilometres. The US began to build the interstate highway (= fast, long-distance road) system in 1956. By 2004 it had more than 42 000 miles/67 578 kilometres of road. The interstate system greatly helped the country's economy, but it also hurt the economies of many small towns not on an interstate. Interstates running north to south have odd numbers and those going from east to west have even numbers. They often have only two or three lanes (= marked sections for lines of traffic) in each direction through the countryside but may have eight or more each way through cities. The New Jersey Turnpike, for instance, has 14 lanes each way near New York City.Other major roads in the US are called superhighways, freeways, expressways, thruways or parkways. There are also many county and local roads, called variously arterial roads, feeder roads or farm roads. Some states have tollways or turnpikes, on which drivers must pay a toll (= sum of money).Interstate highways are marked with red and blue signs showing an ‘I’ followed by the road's number. Other US highways have red, white and blue signs. Some state roads, like those in Louisiana and Texas, have signs in the shape of the state. Since 1995 states have been able to set their own speed limits. This is usually 65 or 70 mph/105 or 112 kph on interstate roads but lower on other main roads.In Britain the fastest and most direct routes between major cities are by motorways, which usually have three lanes of traffic in each direction and a speed limit of 70 mph/112 kph. Each motorway is identified by the letter ‘M’ and a number. Main roads other than motorways are called A-roads and are numbered A6, A34, etc. Some A-roads are dual carriageways with two or more lanes each way. Most A-roads now follow a bypass round towns. Narrower roads which have only one lane in each direction are called B-roads. Most roads have white lines and Catseyes™ (= objects sunk into the ground that reflect a car's lights) down the middle. Only a very few roads have tolls but Britain's first toll motorway, the M6 Toll, opened in 2003 as an alternative to the heavily used M6 near Birmingham. Narrow country roads below B-road standard (called unclassified roads) may be known locally by the name of the place they go to, e.g. Orston Lane. Some country roads may be single track and only wide enough for one vehicle. In this case, there are frequent passing places, where a vehicle can wait to let another through.In Britain the Highway Code describes the many signs placed beside roads. Red circular signs give instructions that must by law be obeyed. These include ‘no overtaking’ signs and signs about speed limits. Red triangular signs give warnings about possible dangers ahead, e.g. slippery roads. Direction signs to major towns are blue on motorways and green on other roads; signs to smaller places are white. Old-fashioned signposts can still be seen in some country areas.In the US red road signs, like ‘Stop’, must be obeyed. Signs that indicate danger, as in areas where rocks might fall, have a yellow diamond shape. Arrows indicating bends in the road are shown in green circles on white signs. Many other US road signs are now similar to those in Europe.In Britain there is pressure from both business and private road users for more and better roads, despite the damage to the environment and increase in pollution that this may cause. People who are against the building of new roads regularly challenge proposed routes of new motorways or bypasses. If they fail, environmentalists (= people who care specially about the environment) may set up protest camps along the route of the new road. Recently, experts too have cast doubt on the wisdom of building more roads, saying it simply encourages greater use of cars. In the US there are few protests against road-building. People generally want more roads to make their journeys faster and more convenient. See related entries: Types of roadExtra examples We were driving down the interstate. You can take Interstate 10 all the way into Baton Rouge. an eleven-car pile-up on the interstate A motorist driving along the interstate saw the plane burst into flames. Speed limits are higher on some rural stretches of interstate highways. There has been an increase in traffic deaths on rural interstates.