the current standards may also be used on the road. The requirements for combinations also include camera systems for side visibility, an advanced emergency braking and lane detector system, electronic driving stability system and electronically controlled brakes. United Kingdom In the United Kingdom, a semi-trailer truck is known as an 'articulated lorry' (or colloquially as an 'artic'). The maximum permitted gross weight of a semi-trailer truck without the use of a Special Type General Order (STGO) is . In order for a 44,000 kg semi-trailer truck to be permitted on UK roads the tractor and semi-trailer must have three or more axles each. Lower weight semi-trailer trucks can mean some tractors and trailer having fewer axles. In practice, as with double decker buses and coaches in the UK, there is no legal height limit for semi-trailer trucks; however, bridges over do not have the height marked on them. Semi-trailer trucks in continental Europe have a height limit of . Vehicles heavier than 44,000 kg are permitted on UK roads but are indivisible loads, which would be classed as abnormal (or oversize). Such vehicles are required to display an STGO (Special Types General Order) plate on the front of the tractor unit and, under certain circumstances, are required to travel by an authorized route and have an escort. Most UK trailers are long and, dependent on the position of the fifth wheel and kingpin, a coupled tractor unit and trailer will have a combined length of between . Although the Construction and Use Regulations allow a maximum rigid length of , this, combined with a shallow kingpin and fifth wheel set close to the rear of the tractor unit, can give an overall length of around . In January 2012, the Department for Transport began conducting a trial of longer semi-trailers. The trial involves 900 semi-trailers of in length (i.e. longer than the current maximum), and a further 900 semi-trailers of in length (i.e. longer). This will result in the total maximum length of the semi-trailer truck being for trailers in length, and for trailers long. The increase in length will not result in the weight limit being exceeded and will allow some operators to approach the weight limit which may not have been previously possible due to the previous length of trailers. The trial will run for a maximum of 10 years. Providing certain requirements are fulfilled, a Special Types