A spare bus earns nothing on a normal day. It sits in the yard, needs insurance, registration and inspections, and loses value. But the morning a route bus fails its pre-trip, a spare is the difference between a late route and a missed one, and many district contracts have penalties for missed runs.
Your spare bus ratio is how many spares you keep for each bus you need on the road. Too few and every breakdown becomes a crisis. Too many and you're paying for buses nobody drives. Here's how to find the right number.
How to work it out
The spare ratio is the number of spare buses divided by the number of buses you need at your busiest time, usually the morning run on a full school day.
| Buses on routes at peak | Spares | Spare ratio |
|---|---|---|
| 10 | 1 | 10% |
| 20 | 3 | 15% |
| 40 | 5 | 12.5% |
| 40 | 8 | 20% |
Many school transportation guides recommend keeping 10 to 15% of the fleet as spares. Transit agencies work to a similar line: the federal transit guideline for large city bus fleets is no more than 20%. There's no single school-bus standard, so treat these as a starting point.
What pushes your number up or down
- Fleet age. Older buses spend more days in the shop. A fleet of 12-year-old buses needs more spares than one of 4-year-old buses.
- Your own shop. A mechanic in the yard turns a bus around the same day. Sending buses out to a vendor means longer waits.
- Special buses. A lift bus covers for a lift bus. If you run wheelchair routes, keep at least one spare that can do them.
- State inspections. Buses come off the road for their inspection days. Plan those for days with fewer runs.
- Field trips and extra runs. If your spares also cover trips, they aren't always free on the morning they're needed.
- Winter. Cold starts, batteries and slippery yards mean more breakdowns from December to February.
- Your contract. Penalties for missed or late runs make a breakdown more expensive than a spare.
Tip: Small fleets need a higher ratio. With 8 routes, one spare is 12.5%, but a second breakdown on the same day leaves you with nothing. Many small contractors keep two spares however small they are.
Checking whether you have the right number
- Count the days you had no spare last school year: a route covered late, doubled up or missed because no bus was free.
- Count the days each spare actually ran. A spare used three days a year is probably one too many.
- Look at why buses were off the road: a few problem buses, or the whole fleet getting older?
- Retire the oldest, least reliable bus before buying a new spare. Often the bus that keeps breaking down is the reason you need one.
Good to know: Your district contract may set its own rules on spare buses, their age and how fast a spare must reach a broken-down bus. Check it before you change your fleet.
Doing it in FleetCommander
Today. The Fleet list has buttons for each status, such as Available, Maintenance and Out of service, each with how many buses have it, and the Dashboard shows how many are ready, in the shop and out of service. The Out-of-service vehicles report lists the buses that are out of service or in the shop, with what is holding them.
Over the year. The Fleet utilization report shows, for each vehicle and the dates you choose, how many Routes it was on, its Days assigned, its Utilization and the Miles it drove. A bus with low utilization all year is a spare in practice, whatever you call it. The Vehicle age report and Maintenance costs show which buses are the oldest and the most expensive to keep. See the Fleet guide and the Reports guide.
Ava (Beta), the assistant in the app, answers Which vehicles are out of service?. More on her page.
Related reading
Questions people ask
- What is a good spare bus ratio for school buses?
- Many school transportation guides suggest 10 to 15% of the buses you need at your busiest time. Older fleets, small fleets and fleets with lift buses often need more.
- How do you calculate a spare bus ratio?
- Divide the number of spare buses by the number of buses needed on routes at your busiest time. Five spares for 40 route buses is 12.5%.
- How many spare buses does a small contractor need?
- Even a small fleet usually keeps at least one or two, so that two breakdowns on one morning don't leave a route without a bus.
- Do spare buses need inspections too?
- Yes. A spare must be inspected, registered and insured like any other bus, and ready to go on the morning it's needed.