In reply to Grim:
I do "train" (ride) on the velodrome, great when the weather is poor. Access isn't always easy here in Glasgow but I can get on for an hour fairly regularly which allows a good session of intervals (10min warm-up, 10x3min efforts with 1min recovery) but a lot of the coach lead sessions are not great for conditioning training.
If you are pushed for time then make that your fall back, quick hour session, whether on the road, track or turbo trainer. You'd not need a HR monitor as it's eye balls out stuff.
In the olden days, as well as the intervals, the session I found most useful were...
Warm-up, 2 hours at just above MaxHR-40beats, warm-down.
Warm-up, 1 hour at just above MaxHR-30beats, warm-down.
The warm-ups, and warm-downs, could be anything from 20min to an hour. Only the bit in the middle was important really.