I worked at Doney Park for four years and got to know the safety rule for riding rides because I operated many thriller rides. As long as read the guidelines before you get on a ride you should be safe.
Must of the roller coasters I operated had guidelines such as should not ride this ride if you had surgery recently, have heart trouble, or have back problems or pregnant you shouldn’t ride this ride. If the customer reads the safety guidelines and has heart trouble and decides to ride the ride with heart trouble and something happens to them I think the customer should take responsibility and not the amusement park.
I even had a few pregnant girls try to ride on roller coasters! Out of the four years of working there I seen many senior citizens ride on roller coasters and other thrill rides, so as long as you READ the SAFETY RULES to each ride before you get on the ride and FOLLOW the rules the ride is very safe.