While driving at a slow/normal speed on a residential road, i went over a gentle speed bump and on the way down, the bottom of the car struck what i believe is part of the roadway. it was a minor bump - but some of the front airbags to deployed. the passenger airbag deployed along with both knee airbags. this was totally unexpected since we were driving at normal residential speeds and slowed for the speed bump. at this speed, whatever it struck on the bottom of the car should not have caused airbag deployment.