WASHINGTON — For a century, the basic idea behind pressing the accelerator on a car has been pretty straightforward. What's going wrong with some Toyotas isn't simple.

Experts say the sudden acceleration problem that has put the brakes on Toyota sales and production is likely not a single problem but an alignment of complicated interconnected conditions.

Nothing illustrates that more than the contradictory statements from the two companies involved. Toyota Motor Corp. is telling the government that it thinks a friction problem in its accelerator pedal mechanisms may make the pedal "harder to depress, slower to return, or, in the worst case, mechanically stuck in a partially depressed position."