Your high-vis jerseys will make you stand out like crazy to cars. That's the point of them, and I have a lot more confidence on the road when I'm wearing them.

Also I find Strava to be pretty accurate. Just divide the distance traveled by your moving time in minutes, then multiply by 60 to see your average MPH. If you're doing 17 then you're way, WAY better than me as I've only gone about 14 average once, and I've ridden over 1,200 miles in the past year. If you doubt the reported distance traveled, then simply check it against a wired or wireless bike computer. Just make sure the computer is properly set with your actual tire's circumference.