Photo courtesy of Pixabay

“Are we there yet?”

The United States is vast. The distance to drive from Portland, Maine to San Francisco, California is about 2725 miles or nearly 4400 kilometers. While the US has many different highway systems, including state, county, territorial, and secondary roads, the country is linked by one massive grid of highways known as The Dwight D. Eisenhower National System of Interstate and Defense Highways. Common English terms for it are freeway, motorway, and expressway. Every driver, however, knows it as The Interstate.

Always expanding and changing, the Interstate began in 1956 as an ambitious project to unite the country. While it is only part of the National Highway System, comprising about 25% of all the traffic, it stretches a total of 48,000 miles across all 48 contiguous states, plus Alaska, Hawaii, and Puerto Rico. It has signs, symbols and, yes, even a language all its own. Understanding that language is important to anyone wishing to travel the country.

The Interstate is a controlled-access highway. This means that it was designed for high-speed vehicular traffic, and all movement of traffic is federally regulated. Speeds, exits and entrances, and traffic lights on the Interstate are federally controlled. So are the shape, color, and numbering of the signage.

Most of the traffic lights on the Interstate, and there aren’t many, are found around toll booths. Drivers must pay a fee at toll booths to continue on the highway. A toll booth operator is a person who takes the money, often making change for the drivers. Many toll booths are automated, and drivers stop to toss in coins or tokens before continuing on. Interstates with tolls are commonly called turnpikes. The New Jersey Turnpike is a system of controlled-access highways running along I-95 through the state of New Jersey.

Interstate highways in the US usually have the highest allowable speed rates in that area. While the average speed might be 55 MPH (which was the maximum allowed for several decades), now 75 MPH is allowed in some rural areas but can go as low as 30 MPH is some more hazardous areas, such as curvy or heavily trafficked areas.

Interstates are also numbered. Primary Interstates are assigned one- or two-digit numbers, while shorter, nearby routes are assigned three-digit numbers where the last two digits match the parent route. We also abbreviate the highways by adding the prefix I– to any Interstate route number. The principle highway in my home state of New Hampshire is Interstate 93, or I-93, but two major adjourning routes, in the cities of Manchester and Concord, are labeled I-293 and I-393 respectively. A  bypass re-routes traffic around a city or congested area.

Cloverleaf photo courtesy of Pixabay

Exceptionally high-traffic areas may have cloverleaf connectors. These elaborate Interstate constructions are highway interchanges where two highways cross over each other. Named for the shape of a four-leaf clover, they have a series of entrance and exit ramps enabling vehicles to proceed in either direction on either highway.

East-West traveling highways have even numbers, while North-South highways end in odd numbers. Thus, I-93 travels South-North from Massachusetts to the Canadian border. The famous Route 66 travelled East-West from Chicago to California.

You will also see mile markers, indicating your location along the Interstate. Mile markers begin at the southern state line for odd-numbered highways, and at the western border for even-numbered highways. Exit numbers at interchanges, where you get off the highway, are either numbered sequentially or are numbered to match the mile marker.

Although many Interstates are in need of repair, they are an essential part of the US national infrastructure. They are also marvels of engineering.