On the Effect on Service Levels of Self Driving Buses

[danieldwilliam]

I am thinking about self-driving vehicles and the impact of them on day to day life. 

I am often on a bus from Chippenham to Calne so I’m using this bus route as the basis for some high-level* thinking about the impact on my life. 

I’m deliberately showing my workings in case** I have made a significant error in my assumptions. 

The service from Chippenham via Calne to Swindon that I use takes about 1 hour 5 minutes one way. It runs every 20 minutes from 6am until 10 pm. A 16 hour service. 

Labour Costs 

I think there will be 5 buses on the route at any one time, one way. Ten buses in total. 

Those buses will need drivers.  Ten drivers.  But they don’t work 16 hours. I reckon they work 8 hour shifts. So two shifts are needed for each day. That’s 15 drivers.   

The drivers will want holidays and will call in sick. I’m guessing about 15% additional headcount to cover absensce.  So that’s 17 and ¼  drivers working this route.  I estimate their salary including on-costs at £30k.  (I’m basing this on adverts I used to see in Swindon for bus drivers.) 

That’s a cost of £520k for direct labour driving the bus. 

Fuel Costs 

The journey is 22 miles one way. 

For three buses an hour each way for 16 hours I make that 96 trips of 22 miles or 2,112 miles per day.  The service doesn’t quite run every day but let’s assume it does.*** 365 days at 2,112 miles per day is 770,880 miles per year. 

Deisel fuel retails at £1.42.  Buses get a rebate of 43p on the fuel duty they pay so the real retail price of the fuel is closer to £0.99.**** 

Fuel costs therefore about £282k per annum. 

Total marginal direct cost for the service £800k  

So of the marginal direct costs 35% (ish) is fuel and 65% (ish) is labour. Shall we say a 3:2 ratio of labour to fuel. 

Sacking all the drivers saves £520k.  

If it helps let me point out that computer driven buses are going to be more fuel efficient than human driven buses.  I’m allowing for a 10% fuel saving, worth £28k. This takes the total cost of the service down to £254k or 32% of its original costs.  Pretty much the third of the cost. 

What conclusions do I draw from this? What is the impact? 

If you were to install a fleet of self-driving buses on the Chippenham to Swindon bus service and sacked all the drivers the savings from driver wages would be about the same the fuel costs for running the service, twice. Therefore you could either triple the frequency or run two equivalent service on a different route***** 

Self-driving buses half or better the cost, double or triple the frequency or double or triple the coverage of bus transport in the UK. 

There are some flaws with the analysis. The most significant is that in order to double the number of bus journeys you need to double or triple the number of buses.  Say £100k per bus. That would be £1.6 million for my Bath to Calne route. Or the savings made in drivers’ wage for 3 years. 

*EDITED*

*To update fuel cost figures for a fuel used per mile more reflective of rural driving conditions* Quite literally your mileage may vary for this post.

 

*Vague and almost certainly wrong but hopefully useful in a Fermi sense. Urban bus labour costs to fuel costs might be significantly different as urban buses are in stop start traffic and the density of buses per route is a bit higher (the routes are shorter and more frequent)

 

**In the expectation 

***The buses will have to be driven back and forwards to the depot and theirs driver training and so on. Let’s call it 365 days. 

**** There are other complexities to do with taxation, especialy VAT but unless you are the Tax manager at my last employer I won’t do VAT for you. 

***** A Bath to Calne route would be my favourite.

Comments

[widgetfox.livejournal.com]

If you're planning to do this on a large scale, I think you might also need to model road capacity.

[f4f3.livejournal.com]

This took me back to primary school mental arithmetic books, for which I do not thank you.

For real world consequences, I'd compare this to what happened when buses went from two-man to one-man operated, when all the conductors got sacked.

So, Michael, what happened when buses went from two-man to one-man operated, when all the conductors got sacked in Glasgow?

Fares stayed the same. Journey frequency stayed the same. No new routes opened up (there's an argument that some routes stayed open that would otherwise have closed sooner).

Vandalism and anti-social behaviour on buses went up (with no conductor to keep the peace, so fewer people used the service.

My guesses, sorry, first order aproximations, would be that no new buses would be bought before the current fleet reached their planned end of life, so we're looking at the difference between a standard and driverless replacement, or, possibly, some retro-fitted kit to existing fleets.

This is driving me (sorry) into thinking about the economics of bus companies. Much like trains, they seem to be reliant on Government franchises. Demand for the service doesn't seem to have a correlation with supply (I heard Coalition politicians talking about how you solved overcrowding on trains by raising ticket prices recently). It seems to me that any reduced costs would not be used for extra services, but to increase profits. Woo hoo!

[naath.livejournal.com]

I often see "twice their salary" as a rough-and-ready estimate of the cost of employing a person - you've got their employer's NI contribs, any pension matching you do, any services you provide to them (subsidised food? office space? toilets?) and so forth. So you probably save more from firing all the drivers than you calculated. Bus companies used to employ two people per bus (a driver and a conductor); perhaps there are good numbers as to how much was saved by reducing the people-per-bus to one.

On the other hand you will have to hire people who can maintain the brain parts of the self-driving buses, which might be on top of the people who maintain other bus parts. There are presumably also costs related to installing the self-drive system, and the bus company would also need a solution to selling and checking tickets. Self-driven buses may also have problems associated with managing the behaviour of bus users and reacting to emergency situations on board (I imagine they would have to be able to react to emergency on-road situations in order to classify as "self driving").

[ice-hesitant.livejournal.com]

Drivers aren't the only kind of labour involved. There's also the invisible but expensive labour of mechanics as well as the necessary janitors to clean them. You also need a garage to house the buses, which can get quite expensive.

[brixtonbrood.livejournal.com]

London under Ken Livingstone did essentially fire all the conductors and double the bus frequency about 10 years ago now, and it boosted the customer useage numbers hugely.

But the important thing to my mind was that it changed the frequency from every 10-20 minute to every 5-10 minutes (in practice, because routes overlap so much, you're normally looking at a maximum 5 minute wait before you get something going in roughly the right direction). That's a hugely significant psychological change in useability. If I'm facing waiting at a bus stop for 20 minutes then I'll drive, or get a convoluted tube or rail journey or take any other choice I have. If I think it's going to be 5 minutes, 10 maximum then I'll go for the bus, especially if it's cheaper, which it is.
The other factor, and the reason he did it, was that the tubes were (and still are) literally full to bursting. At rush hour (roughly 4 hours a day) they run once a minute, and there is no space for any more people at all on many lines. Only buses could increase capacity fast enough to keep the city moving and stop people taking to their cars in desperation (along with congestion charging and increased bike and scooter use of course). And of course there's no point in driving into the centre if finding a parking place is going to take you half an hour when you get there.

The problem with taking the same approach in the countryside is that doubling or trebling frequency normally still leaves service at a level where you won't use it if you have a choice - if service moves from every 2 hours to every 40 minutes then that's excellent news for the people who don't have a choice, but most of the people who do have a choice will still keep driving.

[drifted over here from Andrew Ducker's links]