Trams have a much higher carrying capacity than buses or cars

Note: In the above Triptych, each of the pictures has the same fixed number of people, very spread out in the cars, condensed in the tram.
Expert comments from below  David Walmsley, BSc PhD CMILT MCIHT, Transport Analyst:
Mode Characteristics       Max. capacity (pph)
Car                                        1,000
Bus                                       2,500
Maximum Bus Priority    4,000
Segregated Busway           6,000
Tram                                  12,000

The above World Bank table is accurate for cars for the type of roads into Bath, but is perhaps optimistic for buses and trams, however it does show that trams are much more effective than buses.  More realistic figures are shown in the tables below.

The roads into Bath have a maximum carrying capacity of about 1,000 persons per hour. From the information below we can see that  buses can be 2.5 times more effective as car but trams are 12 times as effective as cars, and about 5 times as effective as buses.
This is why trams can afford to operate at a 6 – 8 minute schedule throughout the day whereas buses have an inherently longer service interval and are more expensive per passenger kilometre, and thus tend to “cherry pick” the the peak time routes.
“These tables are from “What light rail can do for cities,” published by the Passenger Transport Executive Group in 2005 (now called the Urban Transport Group). It’s a pretty comprehensive guide to trams. You can access it on-line at
These are values for vehicles in ordinary urban service. Table 3.1 gives maximum capacities based on a 1-minute headway, showing articulated buses at 7500 and trams at 21,000, but those are not sustainable except in special circumstances.
From David Walmsley, BSc PhD CMILT MCIHT, Transport Analyst:
In the above, it is showing that the three car tram, white, in the centre, can replace 7 buses, and all the cars on the left, ie an 8 lane highway