13.3 Passive Level Crossings 371 In addition to the St. Andrew's cross, in many cases other signals such as text boards are installed immediately in front of the level crossing to warn the road users and give instructions. In many countries, warnings of the approach to level crossings are given by road signs few hundred metres (usually 50 to 250 m, depending on local situation) in advance to give the road user the ability to prepare. In some cases, these signs distinguish between active and passive level crossings or between level crossings with and without barriers. A frequently used form is a triangular road sign with red rim and a steam locomotive or a modern train inside. In the USA, it is a circular sign with a black rim and a black X inside. Frequently the distance between the warning sign and the level crossing is measured by countdown markers with three stripes, two and then one. An example is given in figure 13.2. Besides road signs, the warning of level crossings is often supported by pavement design. Figure 13.2: Road sided warning signs and countdown markers (Sweden as example) Figure 13.1: Forms of St. Andrew's cross on level crossings (not in scale) 13.3 Passive Level Crossings In passive level crossings, the road user is responsible for observing the railway line and recognising an approaching train directly. The most important measure to ensure the perception of the train is to keep the approach sight triangle clear of obstacles. The approach sight triangle is formed as follows, primarily described for the case that the road user is allowed to pass a clear level crossing without stopping or slowing down: As described in chapter 13.1, the road user, when arriving at the permitted speed, must be able to stop at the level crossing when recognising an approaching train. Or, if stopping is not possible because he is already within the stopping distance from the level crossing, he must be able to pass the level crossing safely. The necessary sighting point A (figure 13.3) is the latest point where the road user must decide whether to stop in front of or to pass over the level crossing. It is determined by the stopping distance of the road user, which varies with the initial speed, the braking deceleration and the reaction time of the driver and the vehicle. The neces-
RkJQdWJsaXNoZXIy MjY3NTk=