Roadway Design Manual: Texas Highway Freight Network (THFN)

Section 8: Texas Highway Freight Network (THFN)

Overview

On September 28, 2017 a memorandum was distributed by Bill Hale, P.E. (Chief Engineer) that provided general guidance for the TxDOT Freight Vertical Clearance Policy. The purpose of the Freight Policy is to make Texas the leader in providing movement of freight in the nation. This is a process that should be approached with a long-range vision and plan in place to provide a continuum of efficient Freight movement within the State. Additional consideration and planning should also be given to existing bridges that act as Freight bottlenecks due to low vertical clearances, even if there are no immediate plans for new construction or reconstruction of these bridges. Consideration for exchanging overpasses for underpasses should be given as well.

This policy is applicable to projects that meet the following criteria:

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Let on September 1, 2020 or later;

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Designated as being on the THFN as shown on the THFN map maintained by the Transportation Planning and Programming Division (TPP); and

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Bridge new construction or reconstruction; including bridge widening. BMIP and maintenance projects may not be considered bridge reconstruction, but this would need to be handled on a case-by-case basis in consultation with the Bridge Division. Redecking a bridge will also be handled on a case-by-case basis in consultation with the Bridge Division.

Note, the policy does not apply to THFN overpasses, frontage roads, direct connectors off of the THFN, and entrance and exit ramps that include bridge underpasses. The THFN vertical clearance requirements should be considered for bridge and incidental vertical obstruction to the Freight Network that support significant origin/destination locations.

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Vertical Clearance at Structures

Vertical clearance requirements for roadway structures can be found in Table 2-11.

Minimum vertical clearances for bicycle and pedestrian crossover structures is are increased 1.0-ft from the minimum vertical clearance requirement for vehicular structures due to the increased risk of personal injury upon impact by over-height loads and the relative weakness of such structures to resist lateral loads from vehicular impact.

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Signs, Overhead Sign Bridges (OSB’s), Signals

For the designated THFN, overhead signs shall provide a vertical clearance of not less than the requirement in Table 2-11 to the sign, light fixture, or sign bridge over the entire width of the pavement and shoulders. For traffic signals on the THFN, the bottom of the signal housing and any related attachments to a vehicular signal face located over any portion of a highway that can be used by motor vehicles shall not be less than 0.5-ft below the requirements in Table 2-11. See the latest version of the TMUTCD and applicable TxDOT standards for additional guidance.

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Other Overhead Utilities

All overhead utilities over the designated THFN project must meet the requirements specified in TxDOT’s ROW Utility Manual, Chapter 3.