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Tag: hazard lights

Make your carpool / ride-sharing commute even safer with this amazing plan to add strobe lights to your car—legally! Bicyclists love this one weird tip!

The issue:

One ever-present hazard for bicyclists is the possibility of being “doored”—hit by a suddenly-opened driver’s side door of a parked car.

A similar issue confounds carpool passengers: when exiting a full vehicle, the driver’s-side passenger must open the door directly into traffic (since they cannot exit on the curb side). This presents the obvious risk of being hit by a car that is swerving around the temporarily-parked carpool vehicle, as shown in Figure 1.


Fig. 1: A) The ride-sharing vehicle (blue) is stopped in the farthest-curbside lane, and a passenger is about to exit. A fast approaching-car (red) in the same lane is about to swerve around the parked car. B) The passenger opens the door (purple) and will step out into traffic. C) The red car collides with the open door.

There may be a lot of blame to assign in the scenario in Figure 1 (“the passenger should have waited longer before opening the door” or “the red car shouldn’t have gone around the stopped car”), but it’s easy to see how it would occur without any egregious negligence.


In order to make it obvious that a car door may be opening soon (i.e., that there is an occupant associated with a door of a stopped or nearly-stopped car), the following is proposed:

  • A row of lights are placed on the edges of the car, near the doors. These lights must be easily visible from behind the vehicle.
  • When the door handle is operated, these edge lights flash (see Figure 2). This would provide ~1–2 additional seconds for a driver or bicyclist to react before hitting the door.
  • Optionally, weight sensors in the car seats could detect whether or not someone is likely to exit via a specific door (if there are no passengers in the car, there is no reason for any of the lights to flash except for the ones on the driver’s door). Weight sensors are already used to decide whether or not to deploy passenger air bags, so this wouldn’t be a huge engineering challenge.

Fig. 2: Flashing lights on the edge of the car can notify other drivers and bicyclists that a door might be opening soon (or is actively being opened).


If you own an LED manufacturing plant, you should lobby your local government to make this feature mandatory, and try to avoid letting anyone do any scientific research to determine whether or not it’s actually effective.

PROS: Creates a new source of revenue for the LED light industry.

CONS: It is likely that there would be so many false positives—flashing lights for stopped cars at nearly every intersection, for example—that everyone would tune out these ubiquitous and uninformative warnings.

Never be confused by a signaling bus again, assuming you frequently drive behind buses instead of taking public transit (you monster)


Every vehicle has two turn signals on the back.

These can indicate one of two things:

1) Car is turning left / right.

2) If both lights are blinking: “hazard / emergency / vehicle is stopped in roadway.”


Fig 1: The emergency / hazard lights are usually activated by this button.

The issue:

Unfortunately, distinguishing between the “turn signal” and “emergency” requires that both lights are visible.

See figure 2 for a common example involving a bus that is either stopped at a bus stop (and thus it is safe to go around it to the left) or is signaling that it is about to get into the left hand lane (and thus it is not safe to go around it to the left!).


Fig 2: The scenario in question. The bus’s right-side turn signal is blocked by the blue car. So if you saw this scenario in front of you while driving, you wouldn’t know what the bus was planning to do (Remain stopped? Move into the left lane? Who knows!).

Proposal: Change the rate of blinking for the hazard lights

The solution to this issue is very simple: normal turn signals typically blink with approximately equal time in the “on” and “off” portions of the cycle.

We would keep this behavior the same, but change the “hazard light” blinker pattern to a different pattern (for example, two short blinks, followed by a longer pause).

See figure 3a for a current normal blinker’s behavior, and figure 3b for the proposed revision to emergency lights.


Fig 3a: A standard blinker typically blinks on and off in a regular pattern. The “on” and “off” periods usually take the same amount of time.


Fig 3b: In the proposed change, emergency lights would blink in a distinctive “on / off / on / off   (long pause)  on / off / on / off” pattern. This way, even viewing a single blinker would be sufficient to tell if the vehicle was signaling to change lanes or if it had its emergency blinkers on.


This would probably work! And it does not require any additional hardware in the car (i.e., no additional lights). It would probably add zero cents of cost to the manufacture of a new car.

PROS: Easy to implement, probably would work!

CONS: Too easy!!!