Quite a bad one as it happens, & the death knell for the ride in question & the park (I use the term loosely, it was a hole!) in which it was housed. Back in July 2005 I rode the Jet-Stream at Rhyl Ocean Park (with my Fearless then 4 year old daughter). It was pretty quiet, but as we approached the ride, another couple nabbed the 2 front seats, so we took the back 2 instead & another single rider sat in the middle of the car. The ride had a long station front with 2 cars & as the 1st car leaves the station, the other car moves along from the unload area to the loading side.
I saw it on the track in front of us as we came round the final bend a half second before we ploughed into it. I had enough time to grab my daughter & pull her in close to protect her so she only ended up with a few bruises. I damaged my lower back (Still suffer with it now) & got a few cuts & bruises, the guy in the middle came off much the same. The 2 peeps in the front seats weren't so lucky, & were carted off in ambulances with chest & leg injuries, never found out what happened to them. The staff on the ride didn't know what the hell to do & didn't have phones, just stood there smoking rollies, so I had to call the ambulance myself (after 5 minutes convincing the woman on 999 that yes I was ACTUALLY sat on a coaster that had crashed!), 2 fire engines rocked up 5 minutes later & freed us from the restraints. The park closed forever sometime shortly after.
Mercifully, neither me or my daughter suffered any long term mental issues, we're both still HUGE coaster fans! We're just a little more selective around WHERE we go!