Add some scientists to your survey, we will tear this kind of thing apart regardless of whether we use drugs or not. It's the kind of thinking we're trained to do.
It's probably one of these...
- Trains could crash more, carry less passengers at night/day
- Trains could crash more, carry less passengers in different seasons, either due to weather or light conditions
- " over long and/or dangerous routes
- " during non-rush, as the driver is nearer the end of his shift and less attentive
- Lower passenger trains are likely to be older and shittier and therefore more likely to crash
- Less populated trains get more rookie or elderly conductors
- Shorter trains have less passengers and crash more because they are lighter, harder to drive, older, etc.
- Less populated trains may have left off schedule, making a crash more likely
- Less passengers in overnight trains, which increases driver fatigue
Probably not one of these...
- Weight differences could make the train go faster and crash more easily, or make the driver adjust more poorly
- Trains with less passengers have more dangerous freight that increases the odds of a crash
Getting more silly...
- The driver could see less people getting on and freak out since like most people he apparently believes in clairvoyance... this makes him drive worse and crash
- Enough bodies could be destroyed per crash to make up the difference
ok, enough.