This road trip glossary gathers the names and terms that keep coming up when you plan a drive, from the landmarks of Route 66 to the driving rules in Europe. Each definition links to a guide that covers the topic in more detail.
Contents
Big Sur
Definition: Big Sur is the rugged stretch of the Central California coast between Carmel Highlands and San Simeon, where the Santa Lucia Mountains rise straight out of the Pacific. Highway 1 runs along it, cut into the cliffs above the ocean.
Big Sur has no official boundaries, but the name usually covers the coastal section of California State Route 1 between Malpaso Creek near Carmel Highlands and San Carpóforo Creek near San Simeon, along with the Santa Lucia range behind it. It is often described as one of the most scenic undeveloped coastlines in the United States.
For a long time it was one of the most isolated parts of California. The road that opened it up, the Carmel-San Simeon Highway, took 18 years to build and was completed in 1937. It is now signed as part of Highway 1. In 1966, First Lady Lady Bird Johnson led the official scenic road ceremony at Bixby Creek Bridge, and in 1996 the road became one of the first to be named an All-American Road.
The same cliffs that make the drive spectacular also make it fragile. The highway has been closed many times by landslides: in May 2017, a huge slide at Mud Creek buried the road, which did not reopen until July 2018. Before any Big Sur drive, check road conditions and the status of the state parks you want to visit.
Only a few thousand people live in Big Sur year-round, and lodging is limited to a handful of small settlements. Services are sparse and parking is tight at popular viewpoints, so many travelers base themselves in Carmel, Monterey or the towns further south and drive the coast in daylight.
Further reading: Pacific Coast Highway Road Trip: Big Sur to Malibu Itinerary
Blue Ridge Parkway
Definition: The Blue Ridge Parkway is a scenic mountain road of 469 miles through Virginia and North Carolina, linking Shenandoah National Park to Great Smoky Mountains National Park. It is managed by the National Park Service and is free to drive.
The parkway follows the spine of the Blue Ridge, a range of the Appalachian Mountains. It is a National Parkway and an All-American Road, and it is described as the longest linear park in the United States. At its northern end it connects with Skyline Drive, a similar road through Shenandoah National Park.
Construction began on September 11, 1935, as a New Deal public works project. Most of the road was finished by the end of 1966, but the last section around Grandfather Mountain, including the curving Linn Cove Viaduct, only opened in 1987, more than half a century after work started.
Driving the parkway is slow by design. There are no direct interchanges with interstates, the speed limit never goes above 45 mph, and mileposts count from zero in Virginia to 469 in North Carolina, which makes them handy for locating overlooks and stops. Commercial vehicles need special approval.
The road is not maintained in winter, and high sections and tunnels are often closed from late fall to early spring. Damage can also close it for long periods: the whole parkway was shut in late September 2024 after Hurricane Helene, then reopened section by section. Always check the official closure map before you go.
Further reading: Scenic Road Trips USA: The Best Routes, When to Go, How Long
Cadillac Ranch
Definition: Cadillac Ranch is a public art installation near Amarillo, Texas: a row of ten Cadillacs from 1949 to 1963, buried nose-first in a field. Created in 1974, it has become one of the best-known roadside stops on Route 66.
The work was created by Chip Lord, Hudson Marquez and Doug Michels, members of the art collective Ant Farm. The cars were old runners, used cars or junk, chosen to span successive generations of the model and show the rise and fall of the Cadillac tailfin.
The project was funded by Amarillo businessman Stanley Marsh 3, who placed newspaper ads for used Cadillacs in 1974. The cars originally stood in a wheat field. In 1997 the installation was quietly moved by a local contractor to a new site further from the growing city.
Cadillac Ranch is famous for its ever-changing paint. Visitors are encouraged to spray-paint the cars, which have long since lost their original colors and are covered in layers of graffiti. The site sits on private land, in a pasture along Interstate 40, but visitors are tacitly welcome to walk in through the gate from the frontage road.
Further reading: Route 66 Texas: Shamrock, Amarillo and the Panhandle Stops
Chain of Rocks Bridge
Definition: The Chain of Rocks Bridge is a 1929 bridge over the Mississippi on the northern edge of St. Louis, once used by Route 66. Closed to cars since 1970, it is now open only to pedestrians and cyclists.
The bridge links the Missouri shore to Chouteau Island, part of Madison, Illinois. Its most unusual feature is a 22-degree bend in the middle of the crossing, made necessary during construction by a water intake and by riverbed rock that could not carry the weight of a straight span.
It was built privately as a toll bridge and is now owned by the city of Madison, Illinois. For a time it carried Route 66 across the Mississippi: in the late 1930s, a bypass route of US 66 was signed over the bridge to keep through traffic out of downtown St. Louis.
In 1966 a new bridge was built just to the north to carry I-270, and the old crossing closed to traffic in 1970. After decades of neglect, it was renovated for walking and cycling and is now the northern point of the Mississippi Greenway. It was added to the National Register of Historic Places in 2006.
The name comes from the Chain of Rocks, a series of rocky rapids that made this stretch of the river dangerous for boats. A canal was later dug to bypass the rapids, and a low-water dam built downstream of the bridge now hides most of them except when the river is very low.
Further reading: Missouri Section of Route 66: St. Louis to Joplin Guide
Collision damage waiver
Definition: A collision damage waiver, or CDW, is an optional clause in a car rental contract: in exchange for a fee, the rental company gives up its right to make you pay if the car is damaged or stolen. It is not insurance in the strict sense.
The waiver goes by several names: damage waiver, collision damage waiver or loss damage waiver (LDW). Legally, it is a modification of the rental contract rather than an insurance policy, even though the effect is a transfer of risk from you to the rental company.
Without a waiver, a renter whose car is stolen or damaged by an accident, vandalism or hail may have to pay the full cost of repair, plus administrative charges and, in some states, a fee for the time the car cannot be rented out (loss of use). Some companies also bill towing, storage or the loss in value of the vehicle.
A collision damage waiver does not cover damage you cause to other people or property. That is liability coverage, a separate product. Some US rental companies include the legal minimum liability in the base rate in some states, but not everywhere, so check what your quote actually contains.
Before you accept the waiver at the counter, look at the alternatives. Your own car insurance may extend to rentals, and many credit cards offer some protection against theft and damage when you pay with them. Terms vary widely, so read them before you travel rather than at the desk.
Further reading: Cheap Car Rental for a USA Road Trip: Fees, Insurance, Traps
Dust Bowl
Definition: The Dust Bowl was a period of severe dust storms that ravaged the farms and soils of the American and Canadian prairies in the 1930s. It drove tens of thousands of families west, many of them along Route 66.
The disaster had both natural and human causes: a severe drought, combined with the destruction of the native grasses that held the topsoil in place, by farmers who did not use dryland farming methods to prevent wind erosion. The drought came in waves in 1934, 1936 and 1939 to 1940.
The worst-hit area centered on the Texas and Oklahoma panhandles, reaching into parts of New Mexico, Colorado and Kansas. Families who could no longer grow crops or pay their mortgages abandoned their farms. Many headed for California and were often called Okies, whether or not they came from Oklahoma.
Route 66 became a major route for this westward migration. John Steinbeck's 1939 novel The Grapes of Wrath, which follows a displaced Oklahoma family on the road to California, popularized the highway's nickname, the Mother Road.
The era was also recorded by photographers and musicians. Dorothea Lange documented migrant families, notably in her 1936 photo Migrant Mother, and Woody Guthrie drew on his travels with displaced farmers for his 1940 album Dust Bowl Ballads. Several museums along Route 66 devote exhibits to this period.
Further reading: Route 66 Museum Guide: The Best Stops From Illinois to California
Flash flood
Definition: A flash flood is a sudden flood of low-lying ground, washes, rivers or canyons, usually within a few hours of heavy rain. In the desert Southwest, a storm far away can send a wall of water down a dry wash with little warning.
What sets a flash flood apart from an ordinary flood is speed: there are fewer than six hours between the rainfall and the onset of flooding. They are often caused by severe thunderstorms, hurricanes or tropical storms, but also by melting snow and ice, or by the failure of a natural or man-made dam.
They are common in the arid plains of the Southwestern United States and in high mountain ranges. Dry ground absorbs little water, so rain runs off fast, and a flood can strike miles downstream from where it is raining, under a clear sky.
For drivers, the danger is real. More than half of flash flood deaths involve people swept away in vehicles while trying to cross flooded roads, and about two feet of moving water is enough to carry away most SUV-sized vehicles. The US National Weather Service sums up the advice in four words: Turn Around, Don't Drown.
On a road trip, check the weather forecast for the whole area, not just your stop, before hiking a slot canyon or crossing a dip in the road. Never drive into water whose depth you cannot see, and follow local warnings and closures.
Further reading: Weather Forecast for Road Trip Routes: Tools and Seasons
Great River Road
Definition: The Great River Road is a network of state and local roads that follows the Mississippi River from its source at Lake Itasca, Minnesota, to Venice, Louisiana, through ten states. It is not a single highway but a signed route on both banks.
The route passes through Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi and Louisiana. It once extended north into Canada, which explains the old "Canada to Gulf" wording on its logo.
The project dates back to 1938. Each state has its own commission, and they work together through the Mississippi River Parkway Commission. Planning took decades, and the familiar green-and-white pilot's wheel marker, showing a steamboat inside a ship's wheel, began to appear on the designated roads in the late 1950s.
Several state sections are designated as a National Scenic Byway, and in 2021 eight of the ten state routes were named All-American Roads by the Federal Highway Administration. Because the road switches between numbered highways, county roads and town streets, following the pilot's wheel signs is the easiest way to stay on it.
Further reading: Great River Road Road Trip: The Mississippi From Source to Gulf
Harvey House
Definition: A Harvey House was a railroad restaurant or hotel run by the Fred Harvey Company along the Santa Fe Railway in the American West. Several survive along Route 66, including the Barstow Harvey House in California.
The Fred Harvey Company was founded in 1876 by Fred Harvey to feed the growing number of train passengers. Working with the Atchison, Topeka and Santa Fe Railway, it opened eating houses and hotels at stations across the West and is credited with creating the first restaurant chain in the United States.
The company was known for its standards of food and service, and for its waitresses, the Harvey Girls, who signed strict employment contracts. Their story inspired a 1942 novel and the 1946 MGM musical The Harvey Girls, starring Judy Garland.
In Barstow, the Harvey House was built in 1911 by the Santa Fe Railway as Casa del Desierto, a hotel and depot. Its arcades and colonnades mix Spanish Renaissance and Classical Revival styles. In the 1950s it was listed in the Green Book, the guide to businesses that welcomed African-American motorists.
The station closed in 1973 and the building was later bought by the City of Barstow, then restored after damage from a 1992 earthquake. Today it serves as an Amtrak station and houses city offices, the visitor center, the Western America Railroad Museum and the Route 66 Mother Road Museum.
Further reading: Route 66 Mother Road Museum in Barstow, CA: What to Know
Low emission zone
Definition: A low emission zone is a city area with restricted access for the most polluting vehicles, set up to improve air quality. Cars that do not meet the required standard can be fined if they enter, often after being detected by cameras.
In most low emission zones, there are no barriers: vehicles that do not meet the emission standard are simply fined if they drive in. Many cities enforce the rules with number-plate recognition cameras that check each car against a database. Stricter variants exist, such as zero-emission zones open only to electric and hydrogen vehicles.
In Spain they are called zonas de bajas emisiones (ZBE). Madrid set up its zone in 2018 and Barcelona approved its own in 2020. The climate change law passed in May 2021 requires Spanish cities with more than 50,000 inhabitants to create one.
Spanish rules rely on the environmental label, a colored sticker that classifies vehicles into categories according to their emissions. When you rent a car in Spain, ask which label it carries and check the local rules of each city before driving into its center, since access conditions vary from one zone to another.
Further reading: Spain Road Trip: Andalusia and the Basque Coast Itinerary
Mighty 5
Definition: The Mighty 5 is the name Utah's tourism office uses for the state's five national parks: Zion, Bryce Canyon, Capitol Reef, Canyonlands and Arches. Linking them by car is one of the classic road trips of the American West.
Each park anchors a travel region of southern Utah, with state parks, national monuments and small towns around it. Zion sits near Springdale, Bryce Canyon near Bryce, Capitol Reef near Torrey, and both Arches and Canyonlands are reached from Moab.
The landscapes are very different from one park to the next. Arches holds more than 2,000 natural arches, the greatest concentration in the country. Bryce Canyon is known for its red rock hoodoos among the pines, while Zion is famous for its deep canyon and hikes such as Angels Landing.
Each park charges its own entrance fee, and the America the Beautiful annual pass is accepted at all five. Some activities need a permit or reservation, such as Angels Landing in Zion or the Fiery Furnace in Arches. From 2026, non-US residents aged 16 and over pay an additional fee at Zion and Bryce Canyon unless they hold the non-resident annual pass, so check the current rules on each park's website before you go.
Further reading: Utah Mighty 5 Road Trip: Zion to Arches in 7 to 10 Days
National Scenic Byway
Definition: A National Scenic Byway is a road recognized by the US Department of Transportation for at least one of six intrinsic qualities: archeological, cultural, historic, natural, recreational or scenic. Several sections of historic Route 66 carry this designation.
The National Scenic Byways Program was created by Congress in 1991 to protect scenic but often less-traveled roads and to promote tourism and local economic development. It is run by the Federal Highway Administration.
A road usually has to be a state scenic byway before it can be nominated at national level. The most outstanding routes, which must meet at least two of the six qualities, are designated All-American Roads: they are considered destinations in their own right.
The label does not change how you drive a road, but it supports signage, preservation and promotion. For a road tripper, a scenic byway designation is a good sign that a route is worth a detour, and byway websites often list viewpoints and stops along the way.
Further reading: Historic Route 66: The Mother Road's Story and 2026 Centennial
Overseas Highway
Definition: The Overseas Highway is the 113-mile road that carries US 1 through the Florida Keys to Key West, hopping from island to island over a long series of bridges. Much of it follows the route of a former railroad.
Large parts of the highway were built on the right-of-way of the Overseas Railroad, the Key West Extension of the Florida East Coast Railway, completed in 1912. The railroad was badly damaged by the 1935 Labor Day hurricane, and the company sold the roadbed and the remaining bridges to the state of Florida.
The fully connected highway from the mainland to Key West opened to traffic on March 29, 1938, becoming the southernmost segment of US Route 1. Parts of the road were tolled until 1954, and the route was later realigned and modernized.
The most famous crossing is the Seven Mile Bridge, which links Marathon to the lower Keys. Part of the old bridge next to it is now used by pedestrians and cyclists to reach Pigeon Key, a small island that served as headquarters for the toll district and now has a railroad museum.
Further reading: East Coast Road Trip Ideas: New England to the Florida Keys
Petrified Forest National Park
Definition: Petrified Forest National Park is a national park in northeastern Arizona, known for its fossil logs and the colorful badlands of the Painted Desert. It is the stop where Route 66 travelers can see a preserved stretch of the old road inside a park.
The park is named for its large deposits of petrified wood: fallen trees from the Late Triassic, about 225 million years ago, that turned to stone. The colorful rock layers that hold them belong to the Chinle Formation, which also gives the Painted Desert its name.
The site was declared a national monument in 1906 and became a national park in 1962. Interstate 40, the railroad, the Puerco River and the former Route 66 all cross it from east to west, and the park has preserved a small grassy section of the old highway.
In the northern part of the park, the Painted Desert Inn, a historic museum and bookstore, has been a National Historic Landmark since 1987. The Painted Desert Visitor Center was designed by the modernist architect Richard Neutra. Note that park clocks stay on Mountain Standard Time, since Arizona does not observe daylight saving time.
Further reading: Route 66 Arizona: Kingman, Seligman, Williams and Flagstaff
Vignette
Definition: A vignette is a time-based road charge used in several European countries: instead of paying a toll per distance, you buy the right to use motorways for a set period. It comes as a windshield sticker or, more and more, as an electronic record linked to your plate.
Vignettes are used in Austria, Bulgaria, the Czech Republic, Hungary, Moldova, Romania, Slovakia, Slovenia and Switzerland. In most of these countries they are only needed on motorways and expressways. Several countries have replaced stickers with electronic vignettes.
Switzerland only sells an annual vignette, priced at CHF 40, so even a short transit costs the full-year price. An e-vignette has been available there since August 2023. Austria requires a vignette on its motorways and expressways for vehicles up to 3.5 tonnes and sells short-term options for visitors, including digital vignettes on the official ASFINAG shop.
Driving without a valid vignette can lead to heavy fines, and checks are often made by roadside cameras or officials. Stickers are designed to tear if you remove them, so they cannot be moved to another car. Some tunnels and bridges also charge a separate toll on top of the vignette.
Further reading: Best Road Trip Routes in Europe for American Drivers
ZTL
Definition: ZTL stands for zona a traffico limitato, a limited traffic zone found in many Italian historic centers. Only residents and authorized vehicles may drive in at certain times, and entries are usually checked by cameras.
Limited traffic zones protect historic city centers from heavy traffic, and some also serve to limit pollution. They are especially common in Italy, where around 350 cities have one, but similar zones exist in Spain, Portugal, France and Poland under other names.
Entering a ZTL without authorization is punishable by a fine under the Italian highway code, in addition to the city's own rules. As enforcement relies on camera surveillance, there is no one to stop you at the gate: the penalty arrives later.
The entrance is marked by a square sign with the no vehicles symbol and the words zona traffico limitato, with extra panels showing hours, exceptions or the presence of an electronic gate. Many cities add a display reading ZTL attiva (active) or non attiva. Be careful with the wording varco attivo: it means the restrictions are in force, not that you may go through.
The panels are written in Italian, often in small letters, and are easy to misread when driving. The safest approach is to park outside the historic center and walk in.
Further reading: Italy Road Trip: Dolomites, Tuscany and Amalfi Itinerary