csz The location from which you want to do your search - as far as I know only cities are supported at the moment. You can provide both a zipcode, a city or an address - all seem to work.
mag The level of ‘magnification’. 3 = 4 Miles, 4 = 10 Miles, 5 = 40 Miles
minserv The minimum severity of the traffic condition. 1 = Minor, 2 = Moderate, 4 = Major, 5 = Critical