Ride at least about 76 cm (30 inches) clear of parked cars, and treat anything closer than roughly 2.9 m (9.5 ft) from the curb as a place where a door can still reach you. The first number is a minimum from research; the second is the full reach of the door zone. The practical rule is simple: if you have room to move left without entering a dangerous traffic gap, do it.
What the door zone is
The door zone is the strip beside a parked car that an open door sweeps across. Bike East Bay describes it as the space an open car door extends beyond a car parked at the curb, and the US Federal Highway Administration (FHWA) frames it as the area where riders risk colliding with an open door. Being “doored” means hitting that door, or swerving to avoid it, often into moving traffic.
The measured numbers
FHWA’s study of urban streets gives three figures worth knowing:
| Measurement | Value | What it means |
|---|---|---|
| Minimum riding distance from parked vehicles | 30 inches (about 76 cm) | The distance riders needed to be relatively safe from an opened door |
| Door zone extent, 85th percentile | 9.5 ft (about 2.9 m) from the curb | Covers all but the widest 15 percent of cases in the study areas |
| Parked vehicle and open door | 7 ft to the car’s outside edge plus 2.5 ft of open door | Shows how the 9.5 ft figure is built up |
The “85th percentile” is a common traffic-engineering yardstick: 85 percent of observations fell at or below the value. It is not a guarantee, so a wide door on a large vehicle can still reach farther.
Two numbers, two jobs
- 30 inches is the distance between you and the parked car. It is the figure for how far to ride out from the cars.
- 9.5 ft is measured from the curb, so it includes the width of the parked vehicle. It is the figure engineers use to size a bike lane and its buffer.
Mixing them up leads to mistakes. Riding 30 inches from the car puts your handlebar well inside lane space on a narrow street; riding 9.5 ft from the curb on that same street may put you in the middle of the travel lane.
What other jurisdictions say
The UK Highway Code (Rule 67) tells cyclists to take care passing parked vehicles, leaving enough room, a door’s width or 1 m, to avoid being hit if a door opens, and to watch for pedestrians stepping into their path. That is the UK guidance as read in October 2026; US rules on lane position vary by state, so check your local traffic code. The US and UK figures are close but not identical, and neither is a legal guarantee that you will be safe.
A quick test while riding
Bike East Bay offers an easy check: imagine an invisible friend biking on your right. If there is enough space between you and the parked cars for your friend to fit, you are probably out of the door zone. It works because a rider is about as wide as the clearance you want.
When the bike lane is too narrow
Many painted lanes put you inside the door zone. Bike East Bay advocates a combined bike lane and parking space of at least 14 feet (about 4.3 m), and suggests parking removal, travel lane narrowing or conversion where that is not available. As a rider you cannot fix the street, but you can adapt:
- Ride on the left edge of the lane, even if the paint seems to suggest otherwise.
- Scan for occupied cars: brake lights, a figure in the driver’s seat, or a car that just pulled in.
- Check behind you before moving out, and signal. Our guide to basic rules for cycling on roads covers lane position and signaling.
- Slow down when you cannot get the clearance. Lower speed gives you time to react and lowers the force of a hit.
Riding farther out has a cost: following drivers have to notice and pass you. Bright lights help, and our roundup of commuter bike lights can help you choose some. For route planning, how to commute by bike explains picking streets with fewer parked cars.
What drivers can do
The Dutch Reach is opening the driver’s side door with the right hand, so the body turns and the driver looks back for riders. Dooring is one of the most common forms of bike-car collisions, according to Bike East Bay, so if you drive or take rides, learn the habit. It costs nothing.
When to stop and get help
If you are doored, even at low speed, stop and move out of traffic. Get checked for injuries that appear later, such as head, wrist or hip pain. Before riding again, run through the pre-ride checklist, and have a shop inspect any bent wheel, fork, handlebar or frame. Do not ride a bike with bent or cracked structural parts.
Sources
- US Federal Highway Administration: Pedestrian and bicycle safety research, Chapter 2
- Bike East Bay: Doored
- UK Government: The Highway Code, rules for cyclists 59 to 82
Last reviewed: October 2026.