kaukau describes a cleaner version of CAT Route 109: up Swenson. I would take roughly CAT Route 108: up Maryland Parkway. Either route the traffic will move smoothly and in a fairly direct manner to downtown. The tunnel first takes you south (away from downtown) and then dumps you on the 215, where you can then head north on the 15. I've always seen back ups going from the 215 to the 15, and I've always seen snarls on the 15. Those have been my experiences. YMMV