This post might be useful for others prius owner. I have a prius 2011 Just like every one else i had to be very careful while moving over the speed (car)breaker. Instead of going for spacer as i am not a fan to mess with suspension i went with tyre size increase . Recently after 44k on meter i changed the oem standard yokohama 195 65 R15 Tyre with a Tyre size of 205 65 R15. The difference is 2 % increase and most manufacturer allow less than 3% for safety.
The net result is a near 1 cm increase in height of car that is enough to clear bumps with peace of mind. Yes there is a trade off.Now I need to rev a little more, meaning a couple of notches off my km/l. yet braking and comfort had improved tremendously. (I went with continental contipremiumcontact 5 for top braking and comfort ,on the other hand these tyre have short life)