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Comment by FatalLogic | Hacker News Reader

>#2 The Door Prize: A driver opens his door right in front of you.

If you have time to react to a car door suddenly opening in front of you, is it best to go around the door?

Or should you brake and stop in a straight line, even if you might crash into the door and the person stepping out of the car?

The same site contains a list of cyclist fatalities[0]. In over 95% of the car door collisions, the bicyclist was killed because they swerved or bounced in front of a following vehicle. They were not directly killed by crashing into the door.

But, naturally, that list doesn't include all the times that a cyclist successfully swerved around the door and nothing happened.

[0] https://bicyclesafe.com/doorprize.html

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You'd be surprised how much give car door hinges have. I've managed to almost rip doors off their hinges before when people door me. They are also very surprised when they call the cops as a result of this and receive a ticket for breaking the law.

If somebody opens their car door into the bike lane and after slamming on my brakes, and I can see that I'm not going to stop in time:

1. Try to skid sideways. Your body will impact the door predictably and you will stop. (Same advice when a car pulls a sudden illegal U-Turn.) Having your front wheel impact the door first could result in any number of bad outcomes.

2. Always opt for the door collision instead of swerving out into traffic to avoid the door. The cars behind you are far more deadly than the door is.

No matter the type of collision ALWAYS call 911 and get the driver's information. The police report is key to getting the driver's insurance to pay for your injuries and damage to your bike. You also should always say yes if the 911 operator asks if you need medical attention. You are running on adrenaline and may be in shock after a collision with a car. You will not start hurting until after some time passes.

Then it could be worthwhile practicing that sideways slide maneuver into unexpected obstacles, and always remembering the law is on your side, if there is any law in your country.

[But, like the original bike safety article says, also try not to be so close to stopped vehicles that a door collision can happen]

I think it's similar to car collisions: swerving is tempting because you might prevent the crash, but often taking the crash head on at the lowest speed possible is much safer.

A compounding effect for cyclists is that usually you have a shorter stopping distance in a straight line (since bicycles don't have ABS, so you have to limit breaking while steering)

With or without ABS, stopping distances are shortest when not asking a tire to generate lateral forces as well.

I'd much rather take a low-speed door impact than a high-speed grill impact.

(Same as when you're landing too fast in an airplane: rather continue braking and make a taxi speed tree impact at the end of the runway, rather than open the throttle and end up making the same tree impact at takeoff speed and a few feet in the air.)

But this is why I "swerve" well ahead of parked cars so I can make a smooth, planned transition to the next lane rather than an abrupt sudden one. 99.7 % of the time it turns out to be unwarranted, but sometimes I glad I did it.

> But, naturally, that list doesn't include all the times that a cyclist successfully swerved around the door and nothing happened.

It also doesn't include all of the times cyclists crashed into a door and got back on the bike with nothing but some bruises and a damaged ego. Or any times they crashed and received a noteworthy injury but didn't die.

Like with many safety statistics unfortunately the only data we have to work with is the most severe cases - we have a mountain of data on when things go wrong (deaths), but safe behaviour is invisible since its outcomes are never logged.

Regardless one thing is clear - if you want to avoid either cycling at speed into a person or a heavy metal object, or swerving wildly into passing traffic, always take the lane instead of cycling in the door zone.

> If you have time to react to a car door suddenly opening in front of you, is it best to go around the door?

An ounce of prevention is worth a pound of cure. If you brake, you could run your face through the door window. If you swerve, there better not be a driver behind you.

It's best to be out of the path of the door so you don't have to decide, but I imagine otherwise it's situation dependent. "Am I going fast?", "Is there a huge truck behind me?", etc.

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