pass straight through the station can do so uninterrupted; they do not have to reduce their speed to pass through the curve. This layout is mostly used at local stations where many passenger trains do not stop. Since there is only one passenger platform, it is not convenient to cross two passenger trains if both stop. This type of passing loop is common in Russia and post-Soviet states. A disadvantage of the platform and through arrangement is the speed limits through the turnouts at each end. Up and down working In the example layout shown, trains take the left-hand track in their direction of running. Low-speed turnouts restrict the speed in one direction. Two platform faces are needed, and they can be provided either at a single island platform or two side platforms (as shown). Overtaking is not normally possible at this kind of up-and-down loop as some of the necessary signals are absent. Crossing loops using up-and-down working are very common in British practice. For one thing, fewer signals are required if the tracks in the station are signaled for one direction only; also, there is less likelihood of a collision caused by signalling a train onto the track reserved for trains in the opposing direction. In France, they often use spring switches and the speed is equally restricted in both directions. The speed restriction in one direction can be eliminated with higher-speed turnouts, but this may require power operation, as the longer and heavier high-speed turnouts may be beyond the capability of manual lever operation. Dead-end siding Refuge sidings are used at locations with gradients too steep for heavy freight trains or steam haulage to depart from conventional passing loops, or confined spaces where a passing loop cannot be built. An extra parallel siding is often built at stations on refuge sidings so that two stopping trains can pass, and an extended catch point opposite the refuge siding may be added so as not to interfere with passing trains. Overtaking siding Overtaking loops can also be provided on dual track lines, typically at stations, for the purpose of providing a location for express trains to over take local trains. This layout has extensive use in high-speed rail and East Asian rapid transit systems. In this layout a local train enters the siding allowing a scheduled express train to overtake it. Dynamic passing loop If a crossing loop is