Dear David, 49CFR172.403(c) Transport index ( 1 Meter ) Surface 0 <.5mrem/h = White I >.5mrem/h but not more than 1 >.5mrem/h to 50.0 = Y II >1.0mrem/h but not more than 10 >50mrem/h to 200.0= Y III I Hope this helps. I can fax you a copy of this section if you like. Regards, Tim