Granted, riding around White Rock Lake isn't necessarily the best location for "time trialing," given the multi-use aspect of the place -- but it's certainly nice for speed in lots of places, and the ~9 mile loop is certainly challenging.
I was out at White Rock this morning, and after doing a regular lap, decided to do a "speed lap" based partially on what Tony and others recently posted about the "30-minute lap goal"... However, I was also concerned about pedestrians and overall safety. So, I came up with this counterclockwise run, which helps reduce the number of people you have to pass (or pass close to) --
Start on the west side on Lawther Drive, right where the trail access comes out onto the road. Zero out your computer, and hit it!
Follow the road south, all the way out, not turning onto the railroad bed paved stretch - instead, stay on West Lawther, climbing the "Dolly Parton" hills, turning right and going down to Winstead, and over to the 7-11
At the 7-11, get back on the path, climb the spillway, and stay on the path and street for the normal route along the east side, finishing right where the path from the footbridge comes out on East Lawther.
I rode it, and braked to a quick stop right at the finish point, and read my computer. According to RideWithGPS, this is 8.7 miles. According to my bike computer, it's 8.5 miles. What I LIKE about it, is that it totally avoids the footbridge and winding path at the north end, which is often crowded with walkers and other cyclists. Yes, there are a couple stop signs on West Lawther, and a bit of hill climbing.
May I be so presumptuous as to suggest this be the "standard" speed loop (or speed 'U'), in reference to those wanting to do that kind of self-measurement at White Rock? If so, ride the "U", and use this thread to post your runs... And like I tell the GDB folks about the monthly Mesquite Time Trial that I'm trying to revive, you're not competing against others, you're competing against YOURSELF through the course of the season!
Again, be careful out there -- we're playing in traffic, and WRL is multi-use... be smart, and obey applicable traffic laws...