Chapter 8: Roadbeds

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Section 1: Key Points to Know

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When to Establish Roadbeds

Establish Roadbeds on all segments of a roadway before opening to traffic and before adding data to any segment of the route. This chapter describes the different roadbed classifications, the offices of responsibility, and input instructions.

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Offices of Responsibility

TPP is the Office of Primary Responsibility (OPR) for roadbed processing. Responsibilities include adding, updating, and deleting roadbeds from routes in TRM, according to construction plans or other documents supplied by district offices.

The TRM section of each district office is the Office of Secondary Responsibility (OSR). Each district is responsible for providing TPP with information required to document any constructed roadbeds in the district or for which the district assumes maintenance.

Click this link for your district’s TRM analyst.

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Roadbeds—Driveable roadway segments separated from other roadway segments by any physical barrier including fences, concrete blocks, or other non-driveable surface. Input as From and To Reference Marker limits, although the system stores roadbed segments as “begin roadbed” and “end roadbed” point records.

Begin/End—Identifies the beginning or ending point of a roadbed existing in the data file. Valid values: B (beginning point of specific Roadbed-Id) or E (end point of specific Roadbed-Id).

Id Values—Two-character value identifying a specific roadbed. First character identifies each physically separate roadbed and the second character is always “G—at-grade” (see Figure 7‑1 below). Determine valid values by the roadbed’s function:

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1st Character:


Combination of all mainlane roadbeds K, R, L, S, M, P, T


Single roadbed




Centerline; combination of all roadbed values


Left mainlane road


Right mainlane road


Left supplemental mainlane road (Collector)


Right supplemental mainlane road


Left supplemental supplemental mainlane road


Right supplemental supplemental mainlane road


Left frontage road


Right frontage road


Left supplemental frontage/access road


Right supplemental frontage/access road

2nd Character: G (At Grade)

TRM Roadbed-IDS. (click in image to see full-size image) Anchor: #i998818grtop

Figure 8-1. TRM Roadbed-IDS.

Roadbed-Specific Attributes—Attributes input to certain Roadbed-IDS only.

Width—Measurement, in feet, of the width of the driveable portion of a physically separate roadbed. Portion consists of the driving lanes, including any center turn lanes, and the outside park lanes and/or shoulders. Valid values: 001 to 999.

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