Guide bar

The rubber-tyred metro systems that incorporate 1,435 mm (4 ft 8+1⁄2 in) standard gauge track have angle irons as guide bars, or guiding bars,[1] outside of the two roll ways. The Busan Subway Line 4, that lacks a rail track, has I-beams installed as guide bars. The flanges are vertical. The Sapporo Municipal Subway, that lacks a rail track as well, has no guide bars. It has a central guide rail instead. Guide bars are also used to provide guidance for guided buses.

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  Ouchy M2 station, Showing the angle iron guide bars, the I-beam roll ways and the bumper posts
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  View of a track from a sandpile, in the Montreal Metro near the Beaugrand Station, showing the inverted L cross-section of the guide bars (the extreme flared ends are a fabricated inverse U), precast concrete roll ways and conventional track