Here is more information regarding DOT regulations for Highway Route Controlled Quantities.
As of August 2012 the regulations state:
Subpart D – Routing of class 7 (radioactive) materials
§ 397.101Requirements for motor carriers and drivers.(a) Except as provided in paragraph (b) of this section or in circumstances when there is only one practicable highway route available, considering operating necessity and safety, a carrier or any person operating a motor vehicle that contains a Class 7 (radioactive) material, as defined in 49 CFR 172.403, for which placarding is required under 49 CFR part 172 shall:(1) Ensure that the motor vehicle is operated on routes that minimize radiological risk;(2) Consider available information on accident rates, transit time, population density and activities, and the time of day and the day of week during which transportation will occur to determine the level of radiological risk; and(3) Tell the driver which route to take and that the motor vehicle contains Class 7 (radioactive) materials.(b) Except as otherwise permitted in this paragraph and in paragraph (f) of this section, a carrier or any person operating a motor vehicle containing a highway route controlled quantity of Class 7 (radioactive) materials, as defined in 49 CFR 173.403(l), shall operate the motor vehicle only over preferred routes.(1) For purposes of this subpart, a preferred route is an Interstate System highway for which an alternative route is not designated by a State routing agency; a State-designated route selected by a State routing agency pursuant to §397.103; or both of the above.(2) The motor carrier or the person operating a motor vehicle containing a highway route controlled quantity of Class 7 (radioactive) materials, as defined in 49 CFR 173.403(l) and (y), shall select routes to reduce time in transit over the preferred route segment of the trip. An Interstate System bypass or Interstate System beltway around a city, when available, shall be used in place of a preferred route through a city, unless a State routing agency has designated an alternative route.(c) A motor vehicle may be operated over a route, other than a preferred route, only under the following conditions:(1) The deviation from the preferred route is necessary to pick up or deliver a highway route controlled quantity of Class 7 (radioactive) materials, to make necessary rest, fuel or motor vehicle repair stops, or because emergency conditions make continued use of the preferred route unsafe or impossible;(2) For pickup and delivery not over preferred routes, the route selected must be the shortest-distance route from the pickup location to the nearest preferred route entry location, and the shortest-distance route to the delivery location from the nearest preferred route exit location. Deviation from the shortest-distance pickup or delivery route is authorized if such deviation:(i) Is based upon the criteria in paragraph (a) of this section to minimize the radiological risk; and(ii) Does not exceed the shortest-distance pickup or delivery route by more than 25 miles and does not exceed 5 times the length of the shortest-distance pickup or delivery route.(iii) Deviations from preferred routes, or pickup or delivery routes other than preferred routes, which are necessary for rest, fuel, or motor vehicle repair stops or because of emergency conditions, shall be made in accordance with the criteria in paragraph (a) of this section to minimize radiological risk, unless due to emergency conditions, time does not permit use of those criteria.(d) A carrier (or a designated agent) who operates a motor vehicle which contains a package of highway route controlled quantity of Class 7 (radioactive) materials, as defined in 49 CFR 173.403(l), shall prepared a written route plan and supply a copy before departure to the motor vehicle driver and a copy to the shipper (before departure for exclusive use shipments, as defined in 49 CFR 173.403(i), or within fifteen working days following departure for all other shipments). Any variation between the route plan and routes actually used, and the reason for it, shall be reported in an amendment to the route plan delivered to the shipper as soon as practicable but within 30 days following the deviation. The route plan shall contain:(1) A statement of the origin and destination points, a route selected in compliance with this section, all planned stops, and estimated departure and arrival times; and(2) Telephone numbers which will access emergency assistance in each State to be entered.(e) No person may transport a package of highway route controlled quantity of Class 7 (radioactive) materials on a public highway unless:(1) The driver has received within the two preceding years, written training on:(i) Requirements in 49 CFR parts 172, 173, and 177 pertaining to the Class 7 (radioactive) materials transported;(ii) The properties and hazards of the Class 7 (radioactive) materials being transported; and(iii) Procedures to be followed in case of an accident or other emergency.(2) The driver has in his or her immediate possession a certificate of training as evidence of training required by this section, and a copy is placed in his or her qualification file (see §391.51 of this subchapter), showing:(i) The driver’s name and operator’s license number;(ii) The dates training was provided;(iii) The name and address of the person providing the training;(iv) That the driver has been trained in the hazards and characteristics of highway route controlled quantity of Class 7 (radioactive) materials; and(v) A statement by the person providing the training that information on the certificate is accurate.(3) The driver has in his or her immediate possession the route plan required by paragraph (d) of this section and operates the motor vehicle in accordance with the route plan.(f) A person may transport irradiated reactor fuel only in compliance with a plan if required under 49 CFR 173.22(c) that will ensure the physical security of the material. Variation for security purposes from the requirements of this section is permitted so far as necessary to meet the requirements imposed under such a plan, or otherwise imposed by the U.S. Nuclear Regulatory Commission in 10 CFR part 73.(g) Except for packages shipped in compliance with the physical security requirements of the U.S. Nuclear Regulatory Commission in 10 CFR part 73, each carrier who accepts for transportation a highway route controlled quantity of Class 7 (radioactive) material (see 49 CFR 173.401(l)), must, within 90 days following the acceptance of the package, file the following information concerning the transportation of each such package with the Federal Motor Carrier Safety Administration, Office of Enforcement and Compliance (MC-EC), 1200 New Jersey Ave., SE., Washington, DC 20590-0001:(1) The route plan required under paragraph (d) of this section, including all required amendments reflecting the routes actually used;(2) A statement identifying the names and addresses of the shipper, carrier and consignee; and(3) A copy of the shipping paper or the description of the Class 7 (radioactive) material in the shipment required by 49 CFR 172.202 and 172.203.[57 FR 44131, Sept. 24, 1992, as amended at 66 FR 49874, Oct. 1, 2001; 72 FR 55703, Oct. 1, 2007]