W = 500 (N - 1 + 12N + 36)
where L is the distance between two or more axles, N is the number of axles of a group of axles and W is the weight in pounds, except that two consecutive sets of tandem axles may carry a gross load of 34,000 pounds each if the overall distance between the first and last axle is 36 feet or more.
Or. Admin. Code § 734-073-0080
The Tables referenced are available from the agency.
Stat. Auth.: ORS 184.616, ORS 184.619, ORS 810 & ORS 818
Stats. Implemented: ORS 818.200 & ORS 818.220