I am now outlining a possible design for a high-speed bus which is supposed to run of dedicated high-speed roads or customized roads only. It doesn’t need to have the same small turning circle as an ordinary bus. I am therefore at liberty to make it wider and longer than a bus for present-day roads. In order to allow for a 3+3-seating arrangement in 2nd class, I want to make it 3.5 m wide. That’s almost as wide as the Transrapid, which is 3.7 m wide, I just think that 3.5 m are enough for a 3+3-seating arrangement.
The bus shall be 25-30 m long, about as long as a European passenger train car. With a part of the capacity being used for 1st class seats, in 2+2-seating arrangement, I estimate the total capacity of the vehicle to be around 120 passengers.
A present-day double-deck coach is 4 m high and has a headroom of 1.68 m in the upper deck aisle and of 1.8 m in the lower deck aisle. By removing the upper deck, increasing the headroom of the lower deck to 1.9 m, and accounting for the now missing floor between the upper and the lower deck, I arrive at a height of about 2.35 m for the whole vehicle.
The cross-section of the bus:
I estimate the gross vehicle weight not to exceed 40 tons. A JR 700 Shinkansen car is about as long and has an empty weight of 40 tons. This bus, however, does not need two bogies made from steel which alone account for about 10 tons of weight.
In order to calculate the fuel efficiency, I compare it with an ordinary bus of today, which is 2.55 m wide, 3.5 m high, weighs 18 tons overall and consumes about 25 litres at a speed of 100 km/h. Its drag coefficient is about 0.5, so I calculate a wind resistance of Fw=0.6*0.5*2.55*3.5*(100/3.6)**2=2066 N. Assuming a rolling resistance coefficient of 0.01, I calculate a rolling resistance of Fr=0.01*9.81*18000=1766 N. The total energy consumed per 100 km is therefore W=(Fw+Fr)*v*1 hour=(2066+1766)*(100/3.6)*1 hour=106 kWh.
For the high-speed bus, which is aerodynamically shaped, flatter and wider, I assume a drag coefficient of 0.35. Then its wind resistance at 200 km/h is Fw=0.6*0.35*3.5*2.35*(200/3.6)**2=5331 N, its rolling resistance Fr=0.01*9.81*40000=3924 N. This bus needs only half an hour for a distance of 100 km, therefore I calculate a total energy consumption per 100 km of W=(Fw+Fr)*v*0.5 hour=(5331+3924)*(200/3.6)*0.5 hour=257 kWh, which should result in a fuel consumption of about 61 litres per 100 km.
Given the higher capacity of the high-speed bus compared to ordinary buses of today, the fuel consumption per passenger is about the same. The effect of the aerodynamic shape, the lower height and the greater length offsets the effect of the higher speed. The overall fuel consumption per passenger for a fully-loaded bus is in the magnitude of 0.5 litres per 100 km, which is very low.
The bus should be equipped with a lane keeping system which would allow the high-speed lanes to be made no wider than just about 4 m in straight sections and a bit wider in curves, depending on their radius.
On a dedicated high-speed road with just a single lane, vehicles could easily run at a speed of 200 km/h in headways of only 15 seconds. They would thus run at distances from each other of more than 800 m. Already 400 m would be more than sufficient for braking in the unlikely event that the vehicle in front stopped dead and blocked the road, therefore there is plenty of buffer space in the „timetable“ for dissolving traffic jams after a potential disruption. With headways of just 15 seconds, there could be 240 buses per hour and direction on the road, thus allowing for a capacity of 28800 passengers per hour and direction which is far more than even the busiest long-distance traffic corridor in the world has.
It should also be noted that the lower top speed of 200 km/h is partly offset by the higher service frequency compared to many high-speed railways in the world. Many of them run trains in intervals of no shorter than 1 or even 2 hours, particularly in off-peak time. An interval of 1 hour causes the passenger an average waiting time of 30 minutes. High-speed trains typically have a capacity of at least four times the proposed capacity of the high-speed bus. Therefore, whereas a high-speed train would run at intervals of 1 hour, a high-speed bus would run at intervals of 15 minutes, thus reducing the average waiting to a mere 7.5 minutes. Running 300 km/h instead of only 200 km/h saves 10 minutes per 100 km distance, therefore on distances of up to 225 km the bus would actually be faster.
