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

[danieldwilliam.livejournal.com]

Twice the cost of the salary is probably not a bad rule of thumb if you are making large numbers of people redundant. As you say, on top of the direct on-costs there are all manner of additional organisational costs in HR, legal, training, payroll and so on.

I’ve deliberately not included those because I don’t know enough about the organisational structure of bus companies and the indirect costs could be significantly more or less than I would guess.

Gut feel, the indirect on-costs would be on the low side. We’re talking a fairly homogenous skill set doing fairly routine work so I don’t imagine huge training or back office requirements. But I don’t know.

I’m rolling up the costs of the self-driving system into the capital costs of a new set of buses.

The problems that I think are going to be difficult to sort out are the ones you mention on behaviour of the passengers on the bus. What does the bus do if someone has a heart attack? A bus with a driver might drive to the nearest hospital. Do you install an emergency override? If so, how do you stop idiots hitting it every couple of minutes? Who is the designated leader of the hierarchy and therefore able to tell other people to turn down their ghetto blaster?


There would be software support and some extra hardware to service - and people with the skills to do that will be more expensive to employ than drivers but I think you would need many fewer of them than one per bus.