Except where prefixed with a letter , postmiles was measured on the road as it was when the route was established , based on the alignment that existed at the time , and do not necessarily reflect current mileage . R reflect a realignment in the route since then , M indicate a second realignment , L refer an overlap due to a correction or change , and T indicate postmiles classified as temporary ( for a full list of prefixes , see the list of postmile definitions ) . Segments that remain unconstructed or have been relinquished to local control may be omitted . The entire route is in Riverside County .