Progressively Filtering Options

I am modelling a selection from a product matrix. The customer envisions this as a series of dropdowns, which progressively filters what is available in a subsequent dropdown.

So for example, the first dropdown could be of "Vehicle Type", which shows options for "Car" and "Truck." Then based on the selection, they would choose "Make", and see a series of brands (e.g. Toyota / Ford / Audi). Based on the brand selection, they'd see models... and so on.

  1. Is a series of dropdowns the best job for this? Any alternate option for the UI that is more efficient?

  2. What is the best way to handle when a person makes a series of selections (let's say there are 5 levels in the hierarchy), and then modifies one of the first selections? Is it best to have them "start over"? Or is there a better way to handle it?