The department may require the use of a certified or non-certified escort vehicle(s) in any permit if it determines that public safety so requires. Generally, a certified escort vehicle(s) provision will be included in permits where the vehicle is greater than 12 feet in width; 80 feet or more in length; 14 feet or more in height; with an overhang of 10 feet or more; or where subject to a permit speed restriction. Generally a non-certified escort vehicle(s) provision may be included in permits for self-propelled cranes where the vehicle is over 11 feet in width; 55 feet in length; over legal height; with an overhang of more than 15 feet; which cannot maintain a minimum speed of 45 miles per hour on interstate highways of 30 miles per hour on other highways; or where subject to a speed restriction. A certified escort vehicle(s) requirement may be included in permits for self-propelled cranes when the vehicle significantly exceeds the above limits; where public safety so requires; or where it is likely that traffic control services will be required (i.e., Where vehicle exceeds width of pavement by greater than two feet; vehicle overhang exceeds 50 feet; opposite direction traffic must be controlled to allow for crane movement; road closure is necessary due to highway geometry or similar situations, etc.).