Irvine: First of all, Irvine has fantastic bike paths everywhere, but then there are those pesky intersections to deal with.
For uninterrupted training I ski the Bike path parallel to the 405 Freeway (also known as the San Diego Freeway) between Jeffrey Rd. and Culver in Irvine. The bike path is well placed in the extremely wide right of way to the 405: it’s like your own prairie in there, with the path well back from the road. The cars are just there as background and sometimes entertainment. It is well groomed, and access is easily made to it on a protected path if you park in the small shopping center at the corner of Jeffrey and Alton. This particular stretch is about a mile long, great for laps, and it has a nice elevation change for some grade training.
If like me, you’re comfortable with the occasional passing car, then I highly recommend Yale loop in Irvine. I live on Yale Loop, which is a remarkable feature of city planning; a 4.5- mile long loop with a very wide bike path along it. The intersections are infrequent going clockwise, since most roads to Yale Loop do not pass through. So, one can keep going through a T intersection within the bike path. Yale Loop circumnavigates Irvine’s two man-made lakes, North Lake and South Lake, and it’s quite a nice place to train. Keep your eyes peeled for Barranca. If you get tired and need a burger there’s a Ruby’s (a 50 ‘ s era burger counter restaurant chain… very well done) in the middle of Barranca at the edge of North Lake. -J.E.