Blackdog road down in the river valley might be a good choice for the TT. I'm not sure if it is 3 miles long but it's close. It runs from 35W to Hwy 77. No stop signs or lights except maybe one next to the power station. As far as other routes... You can do river loops between the bridges. I used to go from the Cedar Ave bridge (hwy 77) up Hwy 13, across the Mendota Bridge through Fort Snelling state park to Post Road through the airport area turn South on um... 34th? (past the Hubert Humphrey terminal), along old Shakopee road and eventually back to Hwy 77. There are more options for this route now because it looks like the bike lane accross the 35E bridge is open now, so you could jump from 13 onto the trail that runs down the bluff into the Lillydale regional park and over the 35E Bridge, back on Shepherd Road, accross the HWY 5 bridge (bike lane there also that you get to after Shepherd road turns into the East River Parkway -- steps lead down to the bridge path -- again through Fort Snelling State Park on the other side of the River and then as before...
Loops around the river are nice even for the next month or so (if we are lucky, into November), Lillydale park is gorgeous in the fall.
Although, looking back on your other route I just noticed these are a little west of where you are. I live in St. Paul and have lots of routes that go from near Lake Phalen out towards Stillwater and back. I also have a decent 25 mile loop through the city itself. If you want more specific info go ahead and e-mail me directly. I've been on my bike in most areas of the metro area and things have only continued to better and better as far as routes go. More off road/seperate trails, more bike lanes on roads. There are LOTS of great rides.