Discussion: You can probably use your gps watch

to measure the distance of some straightaway section of low-traffic street to measure out 400 meters to a percent or better, which should be good enough to get a pretty good idea of your pace. You probably aren't getting the endpoints of your quarters on the track to better than a couple of tenths of a second on each end anyhow. Mark the ends with a bit of spray paint near the curb.

your top speed / pace goes to low 5 min/mile - that is mighty good. Need to practice flow at good speed - grab a decent sprint map and try to read and make route choice decisions during high speed at intervals - it is second best to actually running the sprint for practice.

Well, that was my last stab at 400s for awhile and the track should be back in action as of Sept. But it would be nice to have a 400 standard even closer to home, the blocks in our neighborhood are low enough traffic.

Yeah, really need to practice flow/map reading at high speed. I'll get two good trainings in this weekend and I really need to work on doing them at speed. I've gotten some sprint training in recently, but it hasn't been with enough pressure/fast enough. Partly not having controls out slows me down, because I want to be sure and that takes more checks when you get no confirmation. But I'll worry a little less about that this weekend and more about really pushing it!

Maybe Virtual-O would be helpful for sprint training on your own? You can upload gps coordinates exported from a course setting program on to your watch and the watch will buzz when you are close to the locations. I tried it out once in my neighborhood and it worked, seems like it has potential for making training alone easier.

Whoa!! Cool! Need a new Garmin though - currently running with Forerunner 220.

There's also the Orienteering Companion iPhone app which lets you set a course on a real map (you have to calibrate it by going to two known points first) and shows you your position. Works well, probably less handy for trying to train fast.