If you can, use separate routes. My city has three bottlenecks driving all traffic thru three roads to go north into Salem, Peabody or Swampscott. I use one for work/school, one for rec. rides and the last is the fastest and miserable, its for emergencies. It kind of breaks things up for me. Also my rec. rides take me out into quiet wooded roads up to Gloucester or Newburyport. The work/school route is busy roads and red lights. Honestly, I take my "commuter" out on fun rides as often as my roadie.