Life in the fast lane... under the city...
The Subway, Underground, Tube, Metro... whatever you want to call it, you drive it! Go from stop to stop on your line and make sure you reach the next station before the allowed time expires or you'll be penalized - but don't go too fast or you'll forget the people!
There is a set time during which you must get to the next station on the line, but it's not enough to just breeze by, sticking to the schedule is the key. The closest you get to the scheduled time the better, since arriving too early is just as bad as arriving too late.
What's more, you can't forget about the people, they're the reason you're even down here. Each person safely transported to their station of destination yields a bonus. At the end of the line your driving is summarized. You get bonuses for staying on schedule and for every safely transported passanger, and you get penalties for the opposite.
In between shifts you can customize your train. Make enough money and you'll be able to buy a plane ticket to move to another city... to make even more money. Visit and work in the biggest cities around the globe and when you decide it's finally time, buy yourself a one-way ticket to retirement paradise.