Editing Power-to-weight ratio (section)

====Locomotives====
A [[locomotive]] generally must be heavy in order to develop enough [[adhesion railway|adhesion on the rails]] to start a train. As the [[coefficient of friction]] between steel wheels and rails seldom exceeds 0.25 in most cases, improving a locomotive's power-to-weight ratio is often counterproductive. However, the choice of power transmission system, such as [[variable-frequency drive]] versus [[DC motor|direct-current drive]], may support a higher power-to-weight ratio by better managing propulsion power.
{| class="wikitable sortable mw-collapsible mw-collapsed"
|-
! Vehicle
! data-sort-type=number | Year
! data-sort-type=number | Power
! data-sort-type=number | Vehicle weight
! data-sort-type=number | Power-to-weight ratio
|-
| [[Stephenson's Rocket]] [[0-2-2]] [[steam locomotive]] with [[Tender (rail)|tender]]<ref>{{cite encyclopedia|url=http://www.britannica.com/bps/additionalcontent/18/28339806/Robert-Stephenson-and-19thCentury-Transportation-Technology|title=Robert Stephenson and 19th-Century Transportation Technology|encyclopedia=[[Encyclopædia Britannica]]|access-date=2010-01-08|editor-first=Dennis|editor-last=Karwatka|archive-date=2020-04-08|archive-url=https://web.archive.org/web/20200408130521/https://www.britannica.com/bps/additionalcontent/18/28339806/Robert-Stephenson-and-19thCentury-Transportation-Technology|url-status=live}}</ref>
| 1829
| {{convert|15|kW|bhp|abbr=on}}
| {{convert|4,320|kg|lb|abbr=on}}
| 3.5&nbsp;W/kg / 0.002&nbsp;hp/lb
|-
| [[Chicago, Burlington & Quincy]] [[Pioneer Zephyr|Zephyr]] [[streamliner]] [[diesel locomotive]] with [[Railroad car|railcars]]<ref>{{cite journal|url=http://asmcommunity.asminternational.org/vgn-ext-templating/views/ASM/OpenDocument.jsp?vcmid=b6b1a538b5c81210VgnVCM100000621e010aRCRD|access-date=2010-01-12|title=The Burlington Zephyr Stainless Steel Train|first=Harold M.|last=Cobb|date=June 2006|journal=Advanced Materials & Processes|pages=24–28}} {{dead link|date=July 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
| 1934
| {{convert|492|kW|bhp|abbr=on}}
| data-sort-value="94000" | 94&nbsp;[[tonne|t]] / 208,000&nbsp;lb
| 5.21&nbsp;W/kg / 0.003&nbsp;hp/lb
|-
| [[Pennsylvania Railroad Q2 class]] [[4-4-6-4]] [[steam locomotive]] with [[Tender (rail)|tender]] 
| 1944
| {{convert|5,956|kW|bhp|abbr=on}}
| data-sort-value="475900" | 475.9&nbsp;[[tonne|t]] / 1,049,100&nbsp;lb
| 12.5&nbsp;W/kg / 0.0076&nbsp;hp/lb
|-
| [[British Rail Class 43 (HST)|British Rail Class 43]] [[High-speed rail|high-speed]] [[diesel electric locomotive]] 
| 1975
| {{convert|1,678|kW|bhp|abbr=on}}
| data-sort-value="70250" | 70.25&nbsp;[[tonne|t]] / 154,875&nbsp;lb
| 23.9&nbsp;W/kg / 0.014&nbsp;hp/lb
|-
| [[GE AC6000CW]] [[diesel electric locomotive]] 
| 1996
| {{convert|4,660|kW|bhp|abbr=on}}
| data-sort-value="192000" | 192&nbsp;[[tonne|t]] / 423,000&nbsp;lb
| 24.3&nbsp;W/kg / 0.015&nbsp;hp/lb
|-
| [[British Rail Class 55]] [[Napier Deltic]] [[diesel electric locomotive]] 
| 1961
| {{convert|2,460|kW|bhp|abbr=on}}
| data-sort-value="101000" | 101&nbsp;[[tonne|t]] / 222,667&nbsp;lb
| 24.4&nbsp;W/kg / 0.015&nbsp;hp/lb
|-
| [[Bombardier Transportation|Bombardier]] [[JetTrain]] [[High-speed rail|high-speed]] [[gas turbine-electric locomotive]]<ref>{{cite web|url=http://canadair.ca/en/1_0/1_10/1_10_2_1.jsp?menu=1_0|title=Bombardier Transportation&nbsp;– Rail Vehicles&nbsp;– Intercity/Highspeed&nbsp;– JetTrain|access-date=2010-07-24|date=June 2000}}{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
| 2000
| {{convert|3,750|kW|bhp|abbr=on}}
| {{convert|90,750|kg|lb|abbr=on}}
| 41.2&nbsp;W/kg / 0.025&nbsp;hp/lb
|}