U.S.A.

U.K.

An "All-Way Stop" (sometimes a.k.a. a 4-Way Stop)

A crossroads or multiple junction at which traffic from all directions must stop at a 'Stop' sign or a stop line.

Backing Up

Reversing (Americans seemingly never say "reversing")

Bathrooms (at a "Rest Area") --  a.k.a.  "Restrooms"

Toilets

Bicyclist

Cyclist

Cargo Van  (see also "Van" and "Mini-Van")

A van for the carriage of goods

Carpool Lane (a.k.a. a 'Diamond' or 'H.O.V.' Lane)

Lanes restricted to vehicles with multiple passengers

Citation

Being reported by the police for a traffic offence

Commuter Lane

A central lane which is used for traffic in different directions at different times of day, sometimes between movable concrete barriers  (hence the 'zipper' reference, below)

Coupe (pronounced "koop")

Coupé (pronounced 'koop-ay')

Crosswalk

Pedestrian Crossing

Cruiser

Police Patrol Car

Curve

Bend

Diamond Lane (a.k.a. Carpool or H.O.V. Lane)

Lanes restricted to vehicles with multiple passengers

DMV is "Dept. of Motor Vehicles"  (also see RMV)

(Issue drivers' licences and vehicle registrations)

DUI [Driving Under the Influence of alcohol ]

Drunk Driving

DWAI [Driving While Ability Impaired (through alcohol)]

Drunk Driving

DWI [Driving While Intoxicated]

Drunk Driving

Directionals

Indicators

Divided Highway

Dual Carriageway

Defogger

Heated Rear Window

(LCV) Double Trailer

An articulated wagon ("tractor-trailer") with two trailers, in tandem. (Only an LCV if over 80,000 pounds)

Emergency Brake

An inappropriate name for a Handbrake or Parking Brake

Emergency Signals

Hazard Lights

Expressway

Motorway

Flashers (also "Four-Way Flashers" and "Warning Lights)

Hazard Lights

Four-Way

Crossroads

Four-Way Stop  (a.k.a. an All Way Stop)

A crossroads at which traffic from all directions must stop at a 'Stop' sign or a stop line.

Freeway

Dual Carriageway; usually a Motorway equivalent

Full  (or "Full Service") at a "Gas Station"

Attendants will put your petrol in.   Asking for "ten regular" will get you ten dollars worth, not ten gallons

Gas

Petrol  (See "Regular")

Gas Pedal (or just "the gas")

Accelerator

Gas Station

Petrol Station

A "Grade"  (often just a "hill")

Hill

H.O.V. (High-Occupancy Vehicle) Lane (q.v. Carpool)

Lanes restricted to vehicles with multiple passengers

Highway

This generally means a dual carriageway of motorway standards but it can also be used for any road with two or more lanes

Hood

Bonnet

A number, preceded by the letter "I," such as "I-90"

This is an Interstate Highway (q.v.)

Intersection

Any road junction, on major and minor roads

"Interstate," or "Interstate Highway"

Motorway

"Jct 78"  (any number)

Sign on the approach to a junction with the relevant road

LCV ("longer combination vehicle")

An articulated wagon ("tractor-trailer") with either two or three trailers, in tandem. 

("Double Trailers" are only  LCVs if over 80,000 pounds)

Lights

Traffic Lights

Median

Central Reserve

Mini Van  (see also "Van" and "Cargo Van")

A "people carrier" with seats for six or more.

One Way

A One-Way Street or, in some states, the correct side of a Divided Highway (q.v.)

Parkway

Contrary to what it may sound like, it is a road.

Pavement

The road surface. Do not confuse this with Sidewalk!

Pavement Markings

Road Markings (But beware! On the approach to 'Stop' junctions, etc., these are usually absent. Be vigilant.)

"Pike" (as in, for example, the "Mass. Pike")

See 'Turnpike'

R.M.V. is "Registry of Motor Vehicles" (see DMV)

(Issue drivers' licences and vehicle registrations)

Railroad Crossing

A Railway 'Level Crossing'

Ramp

The 'access' or 'exit' slip-road at an 'Intersection'

Regular  (in respect of coffee!)

With milk and sugar! (Massachusetts)

Regular  (in respect of petrol, or "gas")

Unleaded

Rest Area

Usually a proper 'Service Area' (but even on 'Interstates', some are only lay-bys with portable toilets -- no petrol and no food)

Restrooms (at a "Rest Area") --  a.k.a.  "Bathrooms"

Toilets

Rotary

Roundabout (rare or non-existent in many states)

S.U.V. ("Sports Utility Vehicle")

4-by-4's, often similar to Range Rovers, etc.

Sedan

Saloon Car

"Self" (at a "Gas Station")

Self-Service Petrol

A "Semi" (pronounced 'semm-eye') or an "18-wheeler"

Articulated Wagon (a.k.a. as an 'Artic')

Semi-trailer (see just "Semi", above)

Shoulder

The hard shoulder, on the outer edge of the road

Sidewalk

Pavement (but see U.S. "Pavement", above!)

Signals

Traffic Lights

Station Wagon (or just "Wagon")

Estate Car

Stick Shift

Either a manual-transmission car or the actual gear lever

Ticket (a.k.a. a Citation)

Being reported for a traffic offence 

Generally an airport taxiway or even the runway

Tarmac -- Americans may look at you very strangely if you talk about driving on it!

Tractor-trailer 

Articulated Wagon (a.k.a. as an 'Artic')

Traffic Circle

Roundabout (rare or non-existent in many states)

Traffic Signals

Traffic Lights

(LCV) Triple Trailer

An articulated wagon ("tractor-trailer") with three trailers, in tandem.

Trunk

Boot

Turnpike  (often known as the "Pike")

A toll-road, often of motorway standards

U-Turn

A 180º turn (usually in the middle of an intersection!) but be careful, some U.S. states have signs only when this is illegal and in others it is only legal if a sign says you may do it.

Undivided Highway

Single Carriageway

Van  (see also "Mini-Van" and "Cargo Van")

A "people carrier" or MPV with seats for six or more.

Wagon  (as in "Station Wagon)

Estate Car

Warning Lights (also "Four-Way Flashers" and "Flashers")

Hazard Warning Lights

Western Double

Nickname for an articulated wagon ("tractor-trailer") with 2 trailers, in tandem (weight under 80,000 pounds)

Yield

Give Way

Zipper Lane

See 'Commuter Lane'