Editing Light rail (section)

===Comparison with high capacity roads===
One line of light rail (requires 7.6 m, 25' right of way) has a theoretical capacity of up to 8 times more than one 3.7 m (12 foot) lane on a freeway, excluding busses, during peak times. Roads have ultimate capacity limits that can be determined by [[Traffic engineering (transportation)|traffic engineering]], and usually experience a chaotic breakdown inflow and a dramatic drop in speed (a [[traffic jam]]) if they exceed about 2,000 vehicles per hour per lane (each car roughly [[two-second rule (road)|two seconds]] behind another).<ref>Matt Lorenz and [[Lily Elefteriadou]] (2000) [http://onlinepubs.trb.org/onlinepubs/circulars/EC018/08_52.pdf ''A Probabilistic Approach to Defining Freeway Capacity and Breakdown''] (PDF), Transportation Research Board.</ref> Since most people who drive to work or on business trips do so alone, studies show that the average car occupancy on many roads carrying commuters is only about 1.5 people per car during the high-demand [[rush hour]] periods of the day.<ref>{{cite web|title=Highlights of the 2001 National Household Travel Survey: A-15 Vehicle Occupancy Per Vehicle Mile by Time of Day and Weekend Status|url=http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/highlights_of_the_2001_national_household_travel_survey/html/table_a15.html|publisher=US Department of Transportation|access-date=24 February 2016|archive-date=28 June 2017|archive-url=https://web.archive.org/web/20170628142015/https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/highlights_of_the_2001_national_household_travel_survey/html/table_a15.html|url-status=dead}}</ref>
This combination of factors limits roads carrying only automobile commuters to a maximum observed capacity of about 3,000 passengers per hour per lane. The problem can be mitigated by introducing high-occupancy vehicle ([[High-occupancy vehicle lane|HOV]]) lanes and [[ride-sharing]] programs, but in most cases, policymakers have chosen to add more lanes to the roads, despite a small risk that in unfavorable situations an extension of the road network might lead to increased travel times ([[Downs–Thomson paradox]], [[Braess's paradox]]).<ref>https://homepage.rub.de/Dietrich.Braess/Paradox-BNW.pdf (1968) end of chapter 4 retrieved 2023/02/27</ref><ref>{{Cite web|title=Ontario Expanding Highway 401 in Cambridge|url=https://news.ontario.ca/en/release/33297/ontario-expanding-highway-401-in-cambridge|access-date=2 December 2021|website=news.ontario.ca}}</ref><ref>{{Cite web|title=Ontario is finally widening Highway 401 through the GTA|url=https://www.blogto.com/city/2019/04/ontario-widening-highway-401/|access-date=2 December 2021|website=www.blogto.com|language=en}}</ref>

By contrast, light rail vehicles can travel in multi-car trains carrying a theoretical ridership up to 20,000 passengers per hour in much narrower [[Right-of-way (transportation)|rights-of-way]], not much more than two car lanes wide for a [[double track]] system.<ref>Tom Parkinson and Ian Fisher (1996) [http://nrc40.nas.edu/news/blurb_detail.asp?id=2603 ''Rail Transit Capacity''] {{webarchive|url=https://web.archive.org/web/20090111162103/http://nrc40.nas.edu/news/blurb_detail.asp?id=2603 |date=11 January 2009 }}, Transportation Research Board.</ref> They can often be run through [[tramway tracks|existing city streets and parks]], or placed in the [[median (road)|medians of roads]]. If [[Street running train|run in streets]], trains are usually limited by city block lengths to about four 180-passenger vehicles (720 passengers). Operating on two-minute headways using traffic signal progression, a well-designed two-track system can handle up to 30 trains per hour per track, achieving peak rates of over 20,000 passengers per hour in each direction. More advanced systems with separate rights-of-way using [[Moving block|moving block signaling]] can exceed 25,000 passengers per hour per track.<ref>[http://www.trb.org/news/blurb_detail.asp?id=2326 ''Transit Capacity and Quality of Service Manual''], Transportation Research Board.</ref>