UK legislation on buses means that the regulations for double deckers is not as severe as those for single deckers - so much so that some ostensibly single deckers have a passenger comparment downstairs to benefit from this. Or it was the case several years back.

When I travel National Distress to Heathrow there are seat belts and I use them but I do wonder if the flying bodies not belted -in would be as devastating as being thrown around myself. I usually select the front seat (when available) which is arguably not the best option but I do get to see things sooner than others. And no travel sickness.

And the driver is usually on the phone regularly with a "not that free hands free" and one time we took the pretty route in to avoid the M25 junction (where else) that was snarled-up from an accident.