Based on another Jurasdiction (Germany) the main criteria for when seat belt are not required seems to be
- that peaple are allowed to stand during transport
The UK Guidance Seatbelts on urban buses of 2010 confirms this with:
Since 1 October 2001, seat belts have been required to be installed in each forward and rearward facing seat in all new buses. The use of an approved and properly fitted restraint system can help prevent death or serious injury, not only by restraining the occupant from forward motion but also by preventing their ejection from the vehicle, particularly in accidents where the vehicle rolls over.
The only exemption from this requirement is for buses that are designed for urban use with standing passengers. An exemption is permitted for these vehicles because they are typically used for short journeys, in both time and distance, undertaken at moderate speeds on urban routes. Although we are aware that vehicles equipped with seat belts are used by some operators for urban fare paying services, ultimately, it is for the operator to choose the type of vehicle used to provide a service.
So for vehicles that contain seat belts, their usage is required.
Commission Directive 96/36/EC of 17 June 1996 also makes a sole exception using this terminology:
- both urban use and standing passengers
Whereas it is possible to improve the protection provided for passengers against ejection in case of an accident by requiring a minimum of lap belts with retractors for all forward and rear-facing seating positions in motor vehicle sof categories M2 and M3, and in the case of certain M2 vehicles lap and diagonal belts, as foreseen in Directive 90/628/EEC (except those vehicles which are designed for both urban use and standing passengers);
Road Traffic Regulations (StVO)
Section 21a Seat belts, wheelchair restraint systems, wheelchair user restraint systems, protective helmets
(1) Mandatory seat belts must be worn while driving; this also applies to mandatory wheelchair restraint systems and mandatory wheelchair user restraint systems. This does not apply to
- People in door-to-door traffic if they have to leave their vehicle regularly at short intervals in the respective service or delivery district,
- Walking at walking pace such as reversing, driving in parking lots,
- Journeys in buses and coaches which are permitted to carry standing passengers,
- the operating staff in buses and coaches and the accompanying staff of groups in need of special care during the services that require leaving the seat,
- Passengers in buses and coaches with a gross vehicle weight of more than 3.5 t when leaving the seat for a short time.