25 CFR 170.120 - What restrictions apply to the use of an Indian Reservation Road?
Indian Reservation Roads (IRRs) must be open and available for public use. However, the public authority having jurisdiction over these roads may:
(a) Restrict road use or close roads temporarily when required for public safety, fire prevention or suppression, fish or game protection, low load capacity bridges, prevention of damage to unstable roadbeds, or as contained in §§ 170.122 and 170.813;
(b) Conduct engineering and traffic analysis to determine maximum speed limits, maximum vehicular size, and weight limits, and identify needed traffic control devices; and
(c) Erect, maintain, and enforce compliance with signs and pavement markings.