"What will it cost?" is the first question a board asks about a service change. Most of the time, the answer comes from three numbers: buses required, revenue hours, and cost per revenue hour.
Here's how to get each one, on a simple route.
1. Buses required
Start with cycle time: how long one bus takes to run a round trip and be ready to leave again.
Say that your route takes 45 minutes each way, and your recovery policy needs at least 7.5 minutes at each end.
Cycle time = 2 × (45 + 7.5) = 105 minutes.
Divide by the headway and round up. At a 30-minute headway:
Buses required = 105 ÷ 30 = 3.5, rounded up to 4.
Rounding up costs money. Four buses on a 30-minute headway make a 120-minute cycle, so each end now gets 15 minutes of layover instead of 7.5. You pay for that time either way.
2. Revenue hours
In the National Transit Database (NTD), vehicle revenue hours include layover and recovery time. On an all-day route like this one, each bus is in revenue service for the whole span.
Say that the route runs 14 hours on weekdays, 6 a.m. to 8 p.m.
Weekday revenue hours = 4 buses × 14 hours = 56.
Over about 255 weekdays a year: 56 × 255 = 14,280 revenue hours.
3. Cost per revenue hour
Multiply by your cost per revenue hour. Say that it's $150.
Annual weekday cost = 14,280 × $150 = $2,142,000.
Now price the change
Say that the board wants 15-minute service.
Buses required = 105 ÷ 15 = 7. No rounding this time, so layover stays at 7.5 minutes.
Weekday revenue hours = 7 × 14 = 98, or 24,990 a year.
Annual cost = 24,990 × $150 = $3,748,500.
The change adds 3 buses at peak and about $1.6 million a year. Halving the headway raised the cost by 75%. The 30-minute schedule was already paying for an extra 15 minutes of layover per round trip; the 15-minute schedule fits exactly in 7 buses.
What this simple math leaves out
It depends on your system. Four things move the number:
- Fully allocated versus marginal cost. Your NTD cost per hour includes overhead that doesn't grow with one more bus. For a small change, the real added cost is lower. For a large one, overhead grows too.
- Peak versus midday. If the extra buses only run at peak, you still need the vehicles and the operators for that peak.
- Spares and deadhead. Three more buses in service can mean four more in the fleet once you count spares, and deadhead hours cost money without counting as revenue hours.
- Weekends and holidays. Price Saturday and Sunday spans the same way and add them.
The principle
Count buses before you count dollars. On an all-day route, the bus count sets the revenue hours, the operators and the fleet.
What cost per hour does your agency use when it prices a service change: fully allocated, or marginal?
In Transit Planner, this math runs as you draw: buses required, revenue hours and annual cost update for every route, at editable NTD national rates on the Free plan or calibrated to your own published costs on Pro.
