No, because you annihilate your user base on the way.
The number of people willing to pay for subscriptions in this day and age is fairly small compared to the user base that public transport information sites attract. The vast majority of users are not power users - and aren't willing to pay for the one off usage that they will do.
The easiest thing to do is offer an ad-free version for a monthly or annual fee, which would have to be low enough that people wouldn't be concerned about paying, say £2-5 a year. I have no idea if that would cover the 'loss' in not showing ads to that user though.
I have a number of apps where I pay small fees annually on the Play Store and when it's so low, I really don't care (I think one app charges me £1 a year to remove the ads!). I do realise that it all adds up, but some apps do have ads that frustrate and you
need to remove the ads, especially those with an ad that takes focus and needs to be closed. Bustimes isn't one of them though.
Going down the route of limiting features without a sub can ruin the experience and have people stop using it entirely. Too many developers seem to like this option, and it's risky. Some may like an app and pay for the features they're missing, others will find the app too limited and will not be willing to pay (so uninstall it).
I realise bustimes is not an app, but my point still stands. As you say, people aren't going to pay for one-off usage, or something they don't use all the time.