Are flashing brake lights legal?
Yes. Here's why.
SINCE we published details of BMW’s ‘Dynamic Brake Light’ – a system that flashes during heavy braking to warn others you’re hard on the anchors – there’s been some discussion in the comments on whether or not it can be legal in the UK.
So we thought we'd clear it up. The answer, perhaps unsurprisingly, is that it is legal. In fact similar systems have been in use on cars for a few years. While not something that’s detailed in the UK’s own vehicle lighting regulations, the rules around the system are laid out in detail in European regulations that apply in the UK.
BMW’s system flashes its light at a rate of 5hz when the brakes come on hard at speeds over 50km/h (31mph) and goes on to automatically put the hazard lights on if the hard braking continues below 14km/h (9mph). Which matches just what the EU demands.
The key document is E/ECE/324 E/ECE/TRANS/505, Addendum 47, Regulation No. 48, Revision 6, dated June 2010.
Of course.
It’s entitled ‘Uniform provisions concerning the approval of vehicles with regard to the installation of lighting and light-signalling devices’ and, deep within its bowels, is contained the following definition:
2.28. "Emergency stop signal" means a signal to indicate to other road users to the rear of the vehicle that a high retardation force has been applied to the vehicle relative to the prevailing road conditions.
The document goes on to explain that it must be amber or red and that it must be a flashing light, and the automatic application of the hazard lights after an emergency stop is also described.
Further investigation reveals that details for the systems are laid out as follows.
6.23. EMERGENCY STOP SIGNAL
6.23.1. Presence
Optional
The emergency stop signal shall be given by the simultaneous operation of all the stop or direction-indicator lamps fitted as described in paragraph 6.22.7.
[followed by details as to the position and number of the lights]
6.23.7.1. All the lamps of the emergency stop signal shall flash in phase at a frequency of 4.0 ± 1.0 Hz.
6.23.7.1.1. However, if any of the lamps of the emergency stop signal to the rear of the vehicle use filament light sources the frequency shall be 4.0 +0.0/-1.0 Hz.
6.23.7.2. The emergency stop signal shall operate independently of other lamps.
6.23.7.3. The emergency stop signal shall be activated and deactivated automatically.
6.23.7.3.1. The emergency stop signal shall be activated only when the vehicle speed is above 50 km/h and the braking system is providing the emergency braking logic signal defined in Regulations Nos. 13 and 13-H.
6.23.7.3.2. The emergency stop signal shall be automatically deactivated if the emergency braking logic signal as defined in Regulations Nos. 13 and 13-H is no longer provided or if the hazard warning signal is activated.
