If you approach the bridges from Franklin, you can cross at the intersection and if you bike beside the on ramp for heading up towards thickwood you can get on the walkway on the bridge so you don't have to get on the actual roadway. At the end of the bridge there is a trail that curves around and goes underneath all three bridges.
The paved trail that goes up to thickwood near the water treatment plant is still there. It's nice as I wouldn't exactly want to share the road on the bridge as you'd have to ride right in the driving lane. There's almost no shoulder between the driving lane and the guard railing.