Traffic and lights on my route make it tough to get in more than 2-3 minutes of continuous effort without having to ease up or stop.
Some helpful pointers from the USA Cycling Cat6 handbook:
1) All traffic control devices are yields.
2) You are disqualified if you put your feet down on the ground.
3) You are disqualified if it takes more than 5 seconds to hit 25 mph from a legally required stop.