In a tunnel, what distance must a motorcycle rider maintain from the vehicle ahead if they do not intend to overtake it?

When not intending to overtake, a safety distance of at least 100 metres or a minimum interval of four seconds must be maintained at all times from the vehicle ahead. In the case of vehicles whose maximum authorised mass exceeds 3,500 kilograms, the safety distance to be kept from the vehicle ahead must be at least 150 metres or a minimum safety interval of six seconds.