Overpass

<h2 id="history">History</h2>
<p>The world's first railroad flyover was constructed in 1843 by the <a href="/facts/London_and_Croydon_Railway/BagN2lpS">London and Croydon Railway</a> at <a href="/facts/Norwood_Junction_railway_station/QeP3HBY8">Norwood Junction railway station</a> to carry its <a href="/facts/Atmospheric_railway/UjB10rwq">atmospheric railway</a> vehicles over the <a href="/facts/Brighton_Main_Line/kJLgNpLy">Brighton Main Line</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
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<h2 id="highway-and-road">Highway and road</h2>
<p>In North American usage, a <i>flyover</i> is a high-level overpass, built above main overpass lanes, or a bridge built over what had been an <a href="/facts/At-grade_intersection/b51M4MQx">at-grade intersection</a>. Traffic engineers usually refer to the latter as a <i><a href="/facts/Grade_separation/NIs0csjl">grade separation</a></i>. A flyover may also be an extra ramp added to an existing interchange, either replacing an existing <a href="/facts/Cloverleaf_interchange/sed8j53R">cloverleaf</a> loop (or being built in place of one) with a higher, faster ramp that eventually bears left, but may be built as a right or left exit.
</p><p>A cloverleaf or partial cloverleaf contains some 270 degree loops, which can slow traffic and can be difficult to construct with multiple lanes. Where all such turns are replaced with flyovers (perhaps with some underpasses) only 90 degree turns are needed, and there may be four or more distinct levels of traffic. Depending upon design, traffic may flow in all directions at or near open road speeds (when not congested). For more examples, see <a href="/facts/Freeway_interchange/QMSHwNhF">Freeway interchange</a>.
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<h2 id="pedestrian">Pedestrian</h2>
<p>A <a href="/facts/Pedestrian_separation_structure/wgLs0VYl">pedestrian overpass</a> allows traffic to pass without affecting <a href="/facts/Pedestrian/Vc8a4xer">pedestrian</a> safety.
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<h2 id="railway">Railway</h2>
<p>Railway overpasses are used to replace <a href="/facts/Level_crossing/mUGbbLGF">level crossings</a> (at-grade crossings) as a safer alternative. Using overpasses allows for unobstructed rail traffic to flow without conflicting with vehicular and pedestrian traffic. <a href="/facts/Rapid_transit/bbhkQbAW">Rapid transit</a> systems use complete grade separation of their <a href="/facts/Right-of-way_(transportation)/Vzbfroo1">rights of way</a> to avoid traffic interference with frequent and reliable service.
</p><p>Railroads also use <a href="/facts/Balloon_loop/pkt4jQgE">balloon loops</a> and <a href="/facts/Flying_junction/omakQXA4">flying junctions</a> instead of <a href="/facts/Flat_junction/tTLRKKXp">flat junctions</a>, as a way to reverse direction and to avoid trains conflicting with those on other tracks.
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<h2 id="gallery">Gallery</h2>

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Footbridge/tIc9TdGJ">Footbridge</a></li>
<li><a href="/facts/Skyway/6mLrvcHg">Skyway</a></li>
<li><a href="/facts/Stack_interchange/0rs8S2ta">Stack interchange</a></li>
<li><a href="/facts/Viaduct/xAd1mu7L">Viaduct</a></li>
<li><a href="/facts/Wildlife_crossing/pRy1dTPk">Wildlife crossing</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li> Media related to Overpasses at Wikimedia Commons</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Henry K. Evans (1950). "Read the ebook Traffic engineering handbook by Institute of Traffic Engineers". ENGINEERING HANDBOOK, Second Edition 1950. New Haven, Connecticut: Institute of Traffic Engineers. Archived from the original on March 18, 2012. Retrieved October 9, 2010 – via eBooksRead.com. Search for [Separation, Grade]. <a href="https://web.archive.org/web/20120318064658/http://www.ebooksread.com/authors-eng/institute-of-traffic-engineers/traffic-engineering-handbook-hci/page-46-traffic-engineering-handbook-hci.shtml" target="_blank">https://web.archive.org/web/20120318064658/http://www.ebooksread.com/authors-eng/institute-of-traffic-engineers/traffic-engineering-handbook-hci/page-46-traffic-engineering-handbook-hci.shtml</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Turner, J.T. Howard (1977). The London Brighton and South Coast Railway 1. Origins and formation. London: Batsford. p. 249. ISBN 978-0-7134-0275-9 – via Internet Archive. <a href="978-0-7134-0275-9" target="_blank">978-0-7134-0275-9</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
</ol>

Overpass open-in-new

Overpass