Cycling to work - has it been worth it?

I paid 500 quid for my bike + rack + pannier + lock + lights back in September 2006. Since then the only thing I've bought for it has been a carbon fibre handlebar (and I stuck a spare Easton seatpost onto it) but assuming it cost me 500 quid, and given that a return trip on the train is, and has been, 5.30, it was going to take just over 94 commutes to work for it to pay for itself (forgetting about interest, etc etc).

According to my GPS logs, I've ridden it to work and back 50 times thus far. Now, there have been a few times when I couldn't be bothered to log the commute (I have, surprisingly, got better things to do with my time) but that is at least 265 pounds paid off, plus there's the fringe benefits of feeling fitter, not having to be stuck on a train with hundreds of sniffling commuters, almost getting in fights with buses/taxidrivers/policemen/pedestrians, and the smug feeling that you can eat what you like.

But am I really any better off? Well, the obvious question is whether I'm getting any faster or not. The trip home might be a better indicator of this for a few reasons:

• there's often less traffic around than in the mornings


• it's easy to put a fast time in the morning by thrashing yourself, but consistent fitness is going to show up more when you're knackered on the way home, rather than some mad devil-take-the-hindmost duel with a guy on a fixed gear through Lambeth


• er... just because, ok?

Oh dear. Doesn't look like much of an improvement at all, does it? In fact, a trendline through those dots would demonstrate that I've actually slowed down over the last 15 months. Not very impressive, eh?

To cheer myself up, I then considered the moving speed - if this was increasing, then that would mean I was spending more time stuck at traffic lights, but more productive in between. Sadly, that shows that I'm slowing down too. In fact, on pretty much all measures (max speed, average speed, average moving speed) I'm getting worse, not better.

However, I am improving if we consider average speed vs average beats per minute - so as one might expect (or at least hope) as time goes by, I'm getting more efficient at producing speed for a particular exertion (or I'm somehow more efficient and more lazy). So perhaps another resolution for the year should have been to go a bit faster...