Editing MAX Light Rail (section)

===Power and signaling===

MAX is powered by a conventional 750-volt [[direct current]] (DC) [[Overhead line|overhead wire]] system. Most of the system uses a dual-wire catenary, with a [[contact wire]] supported by a [[messenger wire]]. In central city areas such as downtown Portland, however, it uses a single contact wire to minimize the amount of overhead wiring. To further minimize visual impact, ornamental [[street light]] poles, buildings, and bridge structures are used to support the wiring. [[Traction substation|Substation]]s, spaced approximately every {{convert|1|mi|km|spell=in}} apart, convert the high-voltage public supply to the voltage power used by trains. The power system can [[bridge]] any one substation so that trains can continue to operate should a substation or its supply go down.<ref name="power-signals"/>

Approximately 70&nbsp;percent of the MAX system uses [[automatic block signaling]] (ABS),<ref name="power-signals"/> which allows for relatively fast operating speeds—up to {{convert|55|mph|kph|}}—and short [[headway]]s.<ref name="max-blue-line-westside-factsheet-2016"/><ref name="going-to-the-max">{{cite news |last=Federman |first=Stan |title=Going to the MAX: Your ticket to light rail |newspaper=The Oregonian |date=September 5, 1986 |page=T10}}</ref><ref>{{cite news |last=Federman |first=Stan |title=Tri-Met stresses safety of light-rail system |newspaper=The Oregonian |date=September 5, 1986 |page=T7}}</ref> For example, between [[Lloyd Center/Northeast 11th Avenue station]] and Gateway Transit Center along the Banfield Freeway, ABS can accommodate an operating headway of two minutes. Within these sections, [[automatic train stop]]s (ATS) enforce speed limits and automatically apply the [[Railway brake|brake]]s should a train operator fail to do so. The remaining 30&nbsp;percent of the system relies on traffic signals and [[Sightline|line-of-sight]] operation. Speeds do not exceed {{convert|35|mph|kph|abbr=on}} in these sections.<ref name="power-signals"/>