I have worked in transport for over 5 years in software and have read most of the technical books in the internal London Underground library. I generally have read >50 technical books a year.
In my blog I collect and distill what I have learnt. I write about transport, software development and things I feel others should know.
One that I always thought would be interesting is looking at optimisation of the distribution of the Santander Cycle Hire bikes. These are redistributed to expected demand, but movements are costly in terms of people and vans. I spent a week with the team a few years ago and they had a fairly rudimentary modelling system that a university had put together, which involved mostly manual tweaking of routes. This would make for an interesting Kaggle or similar.