Just a follow up -
I bought a Sports Radar LTD SR 3500 with a P2S adapter. I can record readings with a laptop running Hyperterminal and import the data into Excel for analysis. A bit of a kluge, but it was a lot cheaper than a dedicated traffic radar unit.
Two misgivings about the SR 3500: It has a limited range compared to a "real" traffic radar - probably 750 feet or so, and it doesn't distinguish between vehicles coming towards the user, or going away. Some radars will show a negative velocity for an object going away, which helps you tell which vehicle you just measured.
Come to think of it, the limited range may not be so bad - it won't lock onto a semi 1/2 mile away when you point it at the Miata right in front of you.
