about a year ago, i read a news article about police radar and laser systems, which mentioned that modern systems measure not only speed, but also acceleration, and perhaps some other data. the article was of the preachy "look what they've got to catch you with" type, so had no technical details. but i was always curious as to what units they use for acceleration; miles per hour^2 seems like it would be awkward, so perhaps they use (miles per hour) per second . or they could be clever and just call it miles per square minute . does anyone know what they use? come to think of it, car ads often use mixed units (though not quite explicitly) when they boast "0 to 60 [mph] in N seconds". mike