Riding the London bus system at different times (and on different types of buses) got me thinking about optimising bus design. It seems to me that the thing to optimise is people density, i.e. 'number of people per square meter of road'.
There are three basic bus designs in use in London - single-decker,
double-decker and the new 'bendy' buses, which are twice as long but hinged in the middle (and a real pain for other traffic, not to mention that they have an unfortunate tendency to burst into flames).
By the 'people density' measure, bendy buses and single-deckers should be about the same (bendybuses hold more but take up twice as much road space). Doubledeckers would be twice as efficient, except that so much space is taken up by the stairwell. So the challenge would be to come up with a single-decker design that (roughly) doubles people density.
Assuming that a seated person takes up twice as much floorspace as a standing person, a single-decker bus with no seats would achieve this goal. But such buses wouldn't be very popular.
Hence the idea of a bus in which seats can be made to 'disappear' during rush-hour conditions (near the centre of the city, during certain hours, or just under driver control).
The seats are spring-mounted flip-up seats, with the hinge mounted on a horizontal bar at bum-level. A parallel bar runs at waist-height; when the seat flips up, the top end latches to the waist-high bar, preventing it from being lowered. If all seats are raised and latched, the bus has only standing room (two people per seat area), demarcated by the pairs of horizontal bars. As a handy side-effect, the bars stop people being sloshed around inside the bus when it brakes or accelerates.
During non-rush-hour conditions, the driver hits a switch that opens all the latches, allowing the seats to be lowered as required.
As on current buses, certain unlatchable seats would be reserved for people who can't stand.