(a) The Department shall have no power, authority or jurisdiction of the streets of any incorporated city or town, except as otherwise provided in this section, unless such power, authority and jurisdiction shall be voluntarily given and surrendered by such city or town to the Department and then only upon such terms as the Department shall prescribe.
(b) When in the judgment of the Department the route for the construction or reconstruction of any state highway should continue through any incorporated city or town, the Department shall construct and maintain the highway through such incorporated city or town, such construction and maintenance to be at the sole expense of the Department. Whenever the Department shall construct a state highway through any incorporated city or town, it shall not change the widths of the streets of the city or town, except with the consent of the duly constituted governing body of the city or town.
(c) Whenever the Department shall construct a state highway through an incorporated city or town, it shall have the whole and sole control over such construction and over the maintenance of the highway through the city or town, and such highway shall not be undermined, broken open or anywise torn up for any purpose, except by the permit in writing of the Department.
(d) With respect to state highways within their corporate limits, incorporated cities and towns in the State may erect and maintain such traffic control signals as shall be authorized by proper ordinance of the city or town and by the Department.
(e) Local authorities, on the basis of an engineering study and traffic investigation within their respective jurisdictions, may prohibit the operation of trucks or other commercial vehicles or impose limitations as to the weight thereof on designated highways which prohibitions and limitations shall be posted as set forth in § 4505 of Title 21; except that the alteration of weights or the prohibitions of trucks or other commercial vehicles shall not be effective on any state-maintained highway until such alteration has been approved by the Department.
(f) Local authorities, within their respective jurisdictions, may create “historic districts” which encompass 1 or more state-maintained roads, and the standards for traffic signs and traffic markings on any such road may be altered by the Department of Transportation to be more compatible with the time period of the historic district, unless:
(1) The posted speed limit on the road is above 25 miles per hour;
(2) There are more than 2 through-travel lanes on the road;
(3) The road is a U.S. or Delaware route; or
(4) The road has no reasonable alternative route which can adequately handle the traffic.
Any traffic signs or traffic markings that are proposed under this subsection must be approved by the Department of Transportation.
(g) Each rule and regulation adopted pursuant to this section shall be in the form of a resolution signed by the Secretary. A permanent record of these shall be kept by the Department and at the time of adoption a copy of each shall be forwarded to the Department of Safety and Homeland Security, to the New Castle County Police, if within their jurisdiction, and to the incorporated city or town in which the highway lies.
(h) Pursuant to this section, the Department is authorized to perform all engineering studies and traffic investigations necessary to implement this section and Chapter 41 of Title 21, and to install, maintain, operate and remove all traffic-control devices necessary to comply with this section and Chapter 41 of Title 21. Where concurrent authority is granted, the incorporated town or city shall have the responsibility for traffic-control devices.
(i) Nothing in this section shall be construed as granting to the Department or to the local jurisdiction the right to make any rules and regulations respecting the use of highways in incorporated areas contrary to the Code.
Structure Delaware Code
Subchapter III. Jurisdiction, Powers and Duties of Department
§ 132. General powers and duties.
§ 133. Road improvements; additions to state system.
§ 135. Authority to construct dual and express highways.
§ 136. Improvements of roads leading to institutions.
§ 137. Acquisition and sale of real property.
§ 138. Acquisition of uneconomic remnants of land along right-of-way.
§ 139. Notice to landowners; written claim for damages.
§ 140. Educational and safety campaigns.
§ 141. Regulation of traffic; exceptions.
§ 142. Automobile for use of Governor.
§ 143. Expenses of alteration or relocation of facilities or structures of public utilities.
§ 144. Millsboro Pond Dam; construction and maintenance.
§ 145. Corridor capacity preservation.
§ 146. Access to state-maintained highways.
§ 147. Authority to establish standards for traffic-control devices.
§ 149. Authority to adopt regulations governing state land.