Belisha beacons provide additional visibility to zebra crossings for motorists, primarily at night. The UK flash rate is 750 ms on, 750 ms off as per British Standard BS8442-2015, Para 12. Some crossings are set so that each beacon flashes alternately to the other side, but they often fall out of synchronization over time. This has been overcome by the built-in synchronisation and high visibility features included in Belisha beacon patent GB2549455. Beacons with an outer ring of flashing amber LED lights, preferred for their brightness and low electricity consumption, are replacing traditional incandescent bulbs in many areas.