Section 8: Texas Highway Freight Network (THFN)

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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 well thought out 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 due to low vertical clearances act as Freight bottlenecks; 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 (TP&P).
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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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Basic Design Criteria

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Vertical Clearance at Structures

Applicable structures on the THFN project must meet the minimum vertical clearance requirement of 18.5 ft.

Minimum vertical clearances for pedestrian crossover structures is 19.5 ft; this is 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.

The above-specified clearances apply over the entire width of roadway including usable shoulders and include an allowance of 6 inches for future pavement overlays.

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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 19 feet 6 inches 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 be at least 19 feet above the pavement. See the latest version of the TMUTCD for additional guidance.

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Other Overhead Utilities

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

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