Why you get bus jam if you try to run a large city solely on buses only without trams

Above: The picture provided above is  by George Murray shows an Edinburgh bus jam “The classic example of bus jams used to be Oxford Street in London (eased somewhat in recent years) where it was quicker to walk than take a bus and it was virtually impossible to cross the road through a red metal wall, all pouring out PM2.5s by the way).  At its worst, London Transport recorded 239 buses an hour with an average occupancy of 13 pax per bus!”

This is the kind of bus jams London had once trams were removed.  Notice there are no pedestrians crossing the road! For video see here: https://youtu.be/8YmOTx84MWg

Why do you get bus jams?

Trams can have five times the line capacity of a bus so there are far few trams than buses which consequently  don’t impede and  interfere with each other’s movement, wherease with the alternative, 5 more buses, each bus interferes with and holds up the other bus. See below article.

From Professor Lewis Lesley, BSc, AKC, PhD, CEng, MICE, FRSA, FCIT, MTPS

Dear All,
Apart from trams being larger vehicles, so fewer needed to provide the same capacity, being on rails, trams have to operate  strictly to timetable (regular and reliable). The same thing happened when buses replaced trolleybus (‘inflexibly” stuck to their overhead power cables).  When TRRL studied bus unreliability in Bristol, the principal cause was found to be buses leaving terminals not to time table, traffic congestion was only a small part of the problem. The same was a common problem with Dublin buses until real time radio monitoring and regulation was introduced.
As for the proposed reorganisation of buses in Bristol, how much market research has been undertaken with existing passengers, let alone those who do not bus (but drive) ?
Lewis Lesley
Cambridge News

Look at this  article https://www.cambridge-news.co.uk/news/cambridge-news/robin-heydon-column-cambridge-ottawa-13462503 to see how bus jams clog Ottawa “…So obviously, the buses don’t get stuck in the congestion caused by people who still choose to drive. However, they do get stuck in congestion. Bus congestion.  This is basically what Cambridge will look like in a few years time. Changes to Milton Road were recently approved to have longer bus lanes, for up to 60 buses per hour.”

He is what Agatha Christie had to say, in passing, in a 1963 novel “The Clocks”:

” Miss Martindale the typing agency proprietor, looked up from her desk.

‘You’re late back, from lunch Miss Webb.’
‘Sorry, Miss Martindale. There was a terrific bus jam.’
‘There is always a terrific bus jam at this time of day. You should allow for it.’
She referred to a note on her pad.
‘A Miss Pebmarsh rang up……’
Trams have a much higher carrying capacity than buses so you need less of them so not creating a bus jam
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 the type of roads into Bath, but is optimistic for buses and trams, however it does show that trams are much more effective than buses.  David Walmsley, BSc PhD CMILT MCIHT, Transport Analyst.  More tables here: See also: https://bathtrams.uk/relative-carrying-capacity-cars-buses-trams/

Trafic lane priority

Another reason trams don’t get held up is becasue traffic authorities are prepared to grant priotiy to a 300 car tram vs a single car, whereas they are reluctant to do this for little used buses.

Fred has priorities mixed up, why should cars with often only one occupant call the tune and prevent a tram with up to 300 passengers get right of way to allow people to reach their employment on time.  His thoughts are half a century out of date, if everyone travelling to one city centre decided to use a car, grid lock occurs and where are the spaces to park all these cars going to be found?  The single track in George St Croydon had double track in the good old days of Croydon Corporation which was a tight squeeze but with road usage of the time worked well.  The present layout with west bound single track allows for deliveries to retail and the east bound loop by Croydon West Station also works well and is NOT crazy at all.

When the Newhaven extension of the excellent Edinburgh Trams opens in 12 months time it will have double track in an equally narrow Constitution St in Leith which I consider is the correct route and with traffic management will be a success.  Paris tram line 1 has double track in a very narrow street in St Germaine district for the last 27 years and Paris has now nearly ten tram routes.  Trams have the advantage of a guided path to allow safe tolerances in these settings.
Regards George

The problem of bus queues in Princes Street Edinburgh, Cambridge, Oxford

or anywhere that has reasonable demand for public transport arises from the outdated (since the 1930s) British approach of planning a network that goes from everywhere to everywhere to avoid the need to change.  This also relates to our staged fares approach of charging by distance rather than time with no transfer facility.  In mainland Europe ticketing is zonal and even in the biggest cities an extensive travel area is covered by one modestly-priced ticket for all modes with as many changes as required within an hour or 90 minutes.  In most cases return journeys are permitted and day tickets (in fact, usually 24-hour) are valid for up to five travelling together (which explains high use of PT by families where over here we’d get the car out because it really is cheaper.  Public transport has to be simple and no-one can understand complex bus networks in UK urban areas because there are so many overlapping routes.  The classic example of bus jams used to be Oxford Street in London (eased somewhat in recent years) where it was quicker to walk than take a bus and it was virtually impossible to cross the road through a red metal wall, all pouring out PM2.5s by the way).  At its worst, LT recorded 239 buses an hour with an average occupancy of 13 pax per bus!

Green Wave Traffic Ligh Pre-emption

For sound technical reasons, trams generally have city-wide Green Wave Traffic Light Pre-emption which means they do not obstruct each other, buses  generally do not have this, for technical and practical reasons explained here: https://bathtrams.uk/green-wave-traffic-light-pre-emption-is-usually-not-done-for-trams-ie-not-buses-says-world-bank/  This means buses tend to interfere with each other’s  movements and so cause bus jams.