Bicycle Gear-shift Redesign Question

Consider the design of gears and gear shifting controls on modern bicycles, as described below. They are much better than in earlier days, but I claim that the mapping between the actions the gear shifts are supposed to produce and the actions they do indeed produce are unintuitive and require memorization that can interfer with safe operation on the road.

For this question, either defend the current design or describe how the design could be done better. Focus especially on the ideas of mental models and mappings. Assume that you cannot change the physics of the gears -- you can only change the gear shifts. Feel free to be creative with the gear-shift design. You should probably use diagrams to illustrate your answer.

How the bike works:

The front and back gears work together. When the chain is on a small gear in the front, it is easiest to pedal. The rider can modify the degree of easiness by shifting the chain in the back. If the rider has the chain on the largest gear in back, then the bike is in the easiest possible riding situation. As the rider shifts the chain from the larger to the smaller gears in the back, the riding gets a bit more difficult with each gear.

Conversely, if the chain is on the largest gear in the front and the smallest gear in the back, the bike is in the most difficult to pedal situation. To make it a bit easier to pedal, the rider can shift the chain on the read from a smaller to a larger gear, and so on. Thus on the back below there are 8*3 = 24 different difficulty levels.

Detailed illustration:

Back gears: There are eight gears, large to small from the inside out. The larger the gear in the back, the easier it is to pedal.

Front gears: There are three gears, small to large from the inside out. The smaller the gear in the front, the easier it is to pedal. (You can see when I took these photos I had just come up a very steep hill.)

Handlebars: Gear shifts are pressed inwards from either side. Each side has a silver lever which requires a lot of pressure to press inward, and a black lever which is easy to press inward.

Left gear shift: The front gear is controlled by the lefthand gear-shift. Pressing the silver lever (pressing harder) makes it harder to pedal (because it moves the chain on the front to a larger gear). Pressing the black lever inward makes it easier to pedal.

Right gear shift: The back gear is controlled by the righthand gear-shift. Pressing the silver lever (pressing harder) makes it easier to pedal (because it moves the chain to a larger gear, which in the back is easier). Pressing the black lever inward makes it harder to pedal.