Editing Roman bridge (section)

=== Measurements ===
[[File:Sant Angelo bridge.jpg|thumb|left|[[Ponte Sant'Angelo]]]]
Roman bridges were much larger than the bridges of other civilizations. They could be anywhere from {{convert|4.6|to|18.3|m}} long. By the time of [[Augustus]] around the turn of the 1st millennium the maximum span of Roman bridges increased from around {{convert|24|m}} in 142 BC to {{convert|35|m}}.<ref>{{Cite book |last1=Gagarin |first1=Michael |url=https://books.google.com/books?id=lNV6-HsUppsC&q=Bridges+in+Ancient+Rome |title=The Oxford Encyclopedia of Ancient Greece and Rome |last2=Fantham |first2=Elaine |author2-link=Elaine Fantham |date=2010 |publisher=Oxford University Press |isbn=978-0-19-517072-6 |pages=25 |language=en}}</ref> The [[Ponte Sant'Angelo]], built during the reign of [[Hadrian]], has five arches each with a span of {{convert|18|m}}.<ref name="troyano" /> A bridge in [[Alcántara]] has piers {{convert|1|m}} wide, {{convert|47|m}} high, and arches with a span of {{convert|1.3|m}}. Another bridge over the Bibey River in [[Galicia (Spain)|Galicia]] has a pier {{convert|1|m}} wide, arches with a {{convert|4.3|m|adj=on}} span, {{convert|6|and|9|m|adj=on}} side arches, and an arch spanning {{convert|18.5|m}}. Wider spans increase the bridge's drainage, reduce water pressure on the [[spandrels]], and reduced the bridge's weight.<ref name="troyano" /> [[Trajan's Bridge]] over the [[Danube]] featured open-spandrel segmental arches made of wood (standing on {{convert|40|m}} high concrete piers). This was to be the longest arch bridge for a thousand years both in terms of overall and individual span length. The longest extant Roman bridge is the {{convert|790|m|adj=on}} [[Puente Romano]] at [[Mérida, Spain|Mérida]].<ref name=":132">{{harvnb|Galliazzo|1995|pp=92, 93 (fig. 39)}}</ref>