An innovative new bus sound is set to be trialed on London’s latest electric bus route beginning in January.

Transport for London (TfL) developed the sound, which is played through special speakers inside the front of the bus, to ensure that all road users are aware of electric and hybrid buses when they are moving at slow speeds.

Without this sound, these vehicles are almost silent, which could pose a safety risk, particularly for people who are blind or are partially sighted.

The trial on the 100 bus route comes ahead of an artificial sound becoming a regulatory requirement for all new “quiet” running vehicles in 2021.

The sound will play until the bus reaches 12 mph, or when it is reversing or stationary at bus stops. When travelling above 12 mph, the bus will make enough noise that an alert is unnecessary. The pitch of the sound will vary with the speed of the vehicle, helping people know where the bus is and which direction it is going.

The sound will be trialed first at varying volumes on the 100 bus route, which runs between St Paul's Cathedral and Shadwell, over a six-month period from January. It will also be trialed on other routes as new zero-emission vehicles are introduced.

Feedback from road users, residents, passengers, and drivers across all routes will be collected to help develop the most effective system for all road users.

The artificial bus sound is one aspect of TfL's world-leading Bus Safety Standard, which works toward the Mayor's Vision Zero of no deaths or serious injuries on London's roads by 2041.