Better Understanding Transportation Capacity: Roadway vs. Light Rail

Theoretical capacity:
Highway 2,000 to 2,200 vehicles/hour/lane
Major arterial 1,200 vehicles/hour/lane
Headway of light rail 3 minutes (time between trains) or 20 trains/h/track
Train car 200 people per car

Peak hour estimates:
Assume 1.2 persons per passenger car at 2,000 v/h/l = 2,640 p/h/l
Assume 3 minute headway for train = 20 trains per hour per track or 8,000 p/h/track

Consideration: on-street light rail for major arterial
Roadway capacity 1,200 v/h/l at 1.2 passengers = 1,440 p/h/l
Peak hour factor for light rail 0.75 then 6,000 p/h/track (page 5-68, Transit Capacity reference below)
For light rail in US capacity is constrained by demand of 4,000 p/h/track
Reduced street capacity due to light rail = 1,440 p/h/track
Reduced street capacity due to all red phase used by light rail 30 seconds every 3 minutes (light rail headway) or 8.5 minutes per hour (14%) or 204 p/h/track

Comparison for major arterials, two lanes per direction at intersections:
Total intersection capacity 11,520 p/h for automobiles
Total intersection capacity light rail 8,000 p/h
Reduction of intersection capacity 2 lanes (2,880 p/h) and 14% of through traffic in 6 lanes by two tracks (2,448 p/h)

When introducing light rail on a major 2 lane road, the capacity of the road is impacted by reduction of roadway capacity due to dedicated right of way as required for light rail and an all-red phase implemented at signalized street crossings for safety purposes.
It is estimated that the capacity of an intersection of two major arterials with 2 lanes per direction is 11,520 p/h and capacity of light rail for two tracks is 8,000 p/h. Light rail reduces roadway capacity by 1 lane per direction (1,440 p/h/l) and all red phase for six lanes (204 p/h/l/track) thus total roadway capacity reduction due to rail 2,880 p/h and 2,448 p/h (round up to 2,450 p/h).
Net gain/loss of intersection capacity is 8,000-5,330 = 2,670 p/h

Study conducted in Paris for replacing of bus line with tram indicates: 16% of trips per vmt changed from passenger cars to the tram or 3% of car users, welfare losses include 18% of commercial vehicles, shifted 33,750 passenger miles to other roads, increased CO2 by 3,000 ton per year, and 85% of cost borne by region and central government while 57% tram users are Parisians.

Transit Capacity and Quality of Service Manual—2nd Edition
P = Pc Ch (PHF) where:
P = person capacity (p/h)
Pc = maximum design load per car (p/car)
Ch = cars operated per hour (car/h); and
PHF = peak hour factor
Page 58, Exhibit 5-44, Grade Separated Person Capacity Cab Signaling. 2 Light rail train = 10,000 p/h/track
Super Light Rail Vehicles (SLRVs) seat approximately 25 more people than the standard DART Light Rail Vehicle (which seats approximately 75 and has capacity for up to 150 passengers seated and standing).

  • One line of light rail has a theoretical capacity of up to 8 times more than one lane of freeway (not counting buses) during peak times.
  • They usually experience a chaotic breakdown in flow and a dramatic drop in speed (colloquially known as a traffic jam) if they exceed about 2,000 vehicles per hour per lane (each car roughly two seconds behind another).
  • … studies show that the average car occupancy on many roads carrying commuters is only about 1.2 people per car during the high-demand rush hour periods of the day.
  • This combination of factors limits roads carrying only automobile commuters to a maximum observed capacity of about 2,400 passengers per hour per lane.
  • 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 rights-of-way, not much more than two car lanes wide for a double track system.
  • If 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 signalling can exceed 25,000 passengers per hour per track.
  • Most light rail systems in the United States are limited by demand rather than capacity (by and large, most North American LRT systems carry fewer than 4,000 persons per hour per direction), but Boston’s and San Francisco’s light rail lines carry 9,600 and 13,100 passengers per hour per track during rush hour.
Bus Versus Rail: Meta-Analysis of Cost Characteristics, Carrying Capacities, and Land Use Impacts:

  • On average, bus rapid transit (BRT) costs $10.24 million in 1990 dollars per mile to build. This figure is less than half that of that for light rail transit (LRT), $26.4 million and one-tenth of metro rail transit (MRT), $128.2 million. However, in some situations BRT can be more expensive per mile than LRT, and some LRT systems have exceeded the per-mile cost of MRT projects.
  • Compared with LRT systems, bus rapid transit is associated with greater land-acquisition costs ($3.018 million per mile, versus $1.52 million). In addition, dedicated BRT guideways average $6.459 million per mile versus $4.289 million for light rail. Station costs are also slightly higher for BRT than LRT.
  • Bus systems have the lowest cost per vehicle revenue mile and revenue hour, $3.1 and $45, respectively, but the highest cost per thousand passenger mile, $616.4.
  • BRT systems cost per vehicle revenue mile were almost as low as bus systems’, $3.6, and the cost per thousand passenger mile was 24% lower, $496.9.
  • Light rail systems have the highest cost per vehicle revenue mile, $9.3, and the second highest cost per passenger mile, $578.
  • Metro systems cost less than LRT systems per vehicle revenue mile, $6.5; the most per vehicle revenue hour, $152; and the least per thousand place mile and thousand passenger mile, $49.2 and $282, respectively.
  • Buses have the lowest average line capacity per hour, 3,800 to 7,200. BRT can carry 9,000 to 30,000 per hour and LRT can carry 12,200 to 26,900. The highest potential line capacity is of MRT, 67,200 to 72,000.
LOS Capacity Analysis sample
Source of various reports
Substituting a Tramway to a Bus Line in Paris: Cost and Benefits
Page 23, “We obtain: FA = Qa-Ac= 7,760 vehicle*km, or (by multiplying by the occupancy rate) 10,000 passenger*km. These are the passenger*km which have been eliminated. They represent about 16% of the “missing” car passenger*km. The remaining 84 % are undertaken by people who continue to use their cars but on Périphérique or parallel streets.”
Paris walking (61%), cycling (3%), public transport (27%), private motor vehicle (9%) (2010)
NY walking (10%), cycling (1%), public transport (55%), private motor vehicle (29%) (2009)
Dallas walking (2%), cycling (0%), public transport (4%), private motor vehicle (89%) (2009)
Houston walking (2%), cycling (0%), public transport (4%), private motor vehicle (88%) (2009)
Amsterdam (4%), cycling (38%), public transport (30%), private motor vehicle (28%) (2010)

ProjectConnect Urban Rail TV Spot

110 People move to Central Texas every day.
Service 10 to 15 minutes, 7 days a week, 16 station, 4 park and ride

Every day nearly 150,000 commute to the heart of Austin
110 People moving to Austin daily
“Regional vision for transit system”
Routing – East Riverside to Trinity, Red River to 41st, 41st to Hancock (Red Line) to Airport Blvd.
“Provide real alternative to congestion”

Leave a Reply

Your email address will not be published. Required fields are marked *

Translate »