Unfortunately, in a crash involving a bus there is a high chance of people and objects flying about in unpredictable directions. To balance this, they are actually very safe. They tend to travel at a lower speed than a car, and are easy to see. Any crashes tend to be low-damage impacts.

If there are backward-facing seats then these are safer than forward-facing ones, because the bus normally moves forwards. If you have to stand, hold something solid all the time. People who think "defensively" fare better in the event of a disaster: know where the emergency exits are; read the safety notices; try to avoid getting hemmed in by prams and piles of luggage.

I don't think you've got much to worry about on a normal bus trip, to be honest. Millions of people use buses every day and I'm sure the statistics - if you you cared to dig them out - would be very reassuring. By far the most dangerous road users are young men in cars or on motorbikes - reserve your caution for 18-year-old friends who have just got their first car and want to show you how well they drive.