Like a normal driver, if it sees something unexpected or that it doesn't understand, it needs to slow down, drive carefully. No driver steps on the gas if they have something that they don't understand what it is in front of them.
I’d like to see this. Designing behavior and UI presentation for cautious slowdowns would be an interesting challenge. The car would only be slowing in situations when the driver was comfortable (else the driver would be asserting the control.) Believability would be a challenge, as would persuading drivers from setting speed higher to compensate.
