What TfL have provided is a whopping 4266-row database listing "scheduled distances (in metres) and scheduled running times (in minutes) of standard, school, mobility and temporary bus routes, grouped by direction and day type" based on data from May 2021.
» For example we discover that the length of route 8 is 10038 metres from Bus Stop M to St Giles High Street (6.24 miles), but 11123 metres in the opposite direction from New Oxford Street to Bow Bus Garage (6.92 miles).
» For example we discover that route 18 runs from Sudbury to Euston 198 times on weekdays, 186 times on Saturdays and 146 on Sundays.
» For example we discover that route 188 is scheduled on a weekday to take a maximum of 112 minutes to get from Russell Square to North Greenwich, a minimum of 52 minutes and an average of 84 minutes.
So, with a proper official database to browse, I can bring you some definitive lists.
(Direction is important, the figures aren't usually identical in the opposite direction)
London's longest bus routes (daytime) 1)X26 Heathrow → Croydon 24.30 miles 2)465 Dorking → Kingston 16.86 miles 3)166 Epsom → Croydon 16.60 miles 4)111 Heathrow → Kingston 15.99 miles 5)358 Orpington → Crystal Palace 15.75 miles 6)246 Chartwell → Bromley 15.65 miles 7)492 Bluewater → Sidcup 14.83 miles 8)490 Richmond → Heathrow T5 14.34 miles 9)R10 Green Street Green → Orpington 14.32 miles 10)R5 Orpington → Green Street Green 14.32 miles
These are all in south London or around Heathrow. The X26 express is by far London's longest bus route, followed by the Surrey-busting 465 past Box Hill. Only some 166s go all the way to Epsom Hospital - the normal route's six miles shorter. Likewise the 246 in the list is the special summer-Sundays-only Chartwell version - the normal run to Westerham would be in 13th place. Both the R10 and R5 are circulars which TfL measure in two extremely unequal halves (the complete length of one circuit would be 17.03 miles).
The next 10: 314, 463, 407, 232, 331, 229, 607, 455, 216, 969
London's longest night bus routes 1)N199 Trafalgar Square → St Mary Cray 21.92 miles 2)N89 Trafalgar Square → Erith 21.33 miles 3)N9 Heathrow T5 → Aldwych 20.94 miles 4)N68 New Oxford Street → Old Coulsdon 19.74 miles 5)N15 Romford → Oxford Circus 18.75 miles
Night bus routes serving central London tend to be a lot longer than their daytime counterparts, with the N199 to St Mary Cray an absolute whopper. Five other night buses exceed 16.86 miles (the N1, N207, N136, N11 and N8), i.e. they'd all be higher than the 465 in my previous list, i.e. a combined Top 10 of day and night buses would consist of the X26 followed by nine nightbuses. As for the shortest night bus routes, the 238 and 271 are both under five miles.
London's shortest bus routes (official) 1)389 Western Way → Barnet 1.48 miles* 2)327 Waltham Cross → Elsinge Estate 1.70 miles* 3)R9 Orpington → Tintagel Road 1.83 miles* 4)209 Mortlake → Castelnau 1.91 miles 5)399 Hadley Wood → Barnet 1.92 miles* 6)379 Chingford → Yardley Lane 2.05 miles* 7)507 Waterloo → Victoria 2.21 miles 8)346 Upminster → Cranham 2.31 miles* 9)W7 Finsbury Park → Muswell Hill 2.45 miles 10)378 Putney Bridge → Mortlake 2.58 miles
These are the usual suspects, mainly on small peripheral routes, headed by the piddly 389 in Barnet. The 209 and 378 are both affected by the closure of Hammersmith Bridge so their data's only temporary. Routes with asterisks are circular so again the distances are somewhat arbitrary based on when the driver flips the blind. I prefer to average the two unequal halves to give a more realistic measure, indeed that's how I blogged London's shortest bus routes in January 2019, in which case my Top 10 would be 389, 327, 209, 507, 379, W7, 378, R9, 497, 346.
The next 10: 129, 399, E1, 323, 521, 330, 268, 291, 72, 100
The average London bus route is 8.2 miles long.
Half of London's bus routes are between 6½ and 10 miles long.
London's most frequent bus routes 1)38 Hackney Central → Victoria 243 buses per day* 2)507 Victoria → Waterloo 216 buses per day 2)73 Stoke Newington → Oxford Circus 216 buses per day 4)521 Waterloo → London Bridge 214 buses per day 5)W7 Muswell Hill → Finsbury Park 210 buses per day 6)18 Euston → Sudbury 201 buses per day 7)29 Trafalgar Square → Wood Green 199 buses per day 8)453 Deptford → Marylebone 181 buses per day 8)207 Hayes → White City 181 buses per day 10)390 Archway → Victoria 180 buses per day 10)149 Edmonton → London Bridge 180 buses per day
The 38 and 73 have long been super-frequent services plugging tube-free gaps in Islington and Hackney, while the 507 and 521 are highly-focused rush hour connectors for officefolk. The 38's figure is complicated on weekdays with only 60% of journeys running all the way to Clapton Pond and 40% stopping short at Hackney Central, but the Saturday total of 219 still beats all the other routes in the list. To me the most surprising absence is the once pre-eminent 25 which was neutered a few years ago and no longer even appears in the Top 40.
The next 10: EL1, 472, W3, 55, 158, 36, 41, 109, 86, 8
These are fastest timetabled journeys, likely early in the morning or late at night when traffic's at its lightest. Those marked with asterisks are unequal circular routes, so a bit iffy, and the other two routes are Hammersmith Bridge fodder. Top of the heap is the R9 in Orpington which flips its blind just four minutes after setting off so counts as London's briefest journey. In heavy traffic the R9 is timetabled to take 13 minutes to do the same two mile journey, which just goes to show how variable timings on some routes can be.
The average timetabled duration of a London bus is 48 minutes.
London's longest bus routes (duration) 1)X26 Heathrow → Croydon 143 minutes 2)188 Russell Sq → North Greenwich 112 minutes 3)111 Heathrow → Kingston 105 minutes 4)25 Holborn → Ilford 104 minutes 4)341 Waterloo → Meridian Water 104 minutes
These are slowest timetabled journeys, all of them during peak hours when jams slow the traffic in one particular direction. Other routes which are sometimes scheduled to take more than 100 minutes are the 55 (out of town), the 43, 53 and 176 (into town), the 102 and 425 (eastbound), the 57, 358 and G1. The X26 is the only route to top 100 minutes on most journeys, not just a few of them.
London's slowest bus routes (average speed) 1)11 Liverpool Street → Fulham 4.5 mph 2)14 Putney → Russell Square 4.7 mph 3)22 Oxford Circus → Putney 5.0 mph 3)58 East Ham → Walthamstow 5.0 mph 5)8 Bow Church → Tottenham Ct Rd 5.1 mph
These are slowest average speeds at the cloggiest time of day, found by dividing distance by time. The slowest three all crawl between central London and the Chelsea area, which can't be a coincidence. The 58 is unusual because its slowest timetabled speed is on a Saturday, not a weekday. London's fifth slowest bus departs from Bus Stop M at around half past eight in the morning. These are godawful average speeds, although it's not always this bad... for example the 11 gets up to 10mph at the fastest times of day.
The average timetabled speed of a London bus is 10½ miles per hour.
Ignore the R9, it's being anomalous again (no other route can beat 1.8 miles in 4 minutes). The other speediest buses all have significant rural sections with few people to stop for, so get there quicker. Altogether 25 different bus routes manage an average speed over 20mph at certain times of day (but not normally).
London's newest bus route (3 months) 1)456 Crews Hill → North Middlesex Hospital 9.7 miles in 52 minutes
