A TCP design should be of sufficient width so that oversize vehicles permitted to operate on Texas highways can clear any obstructions by at least one foot, particularly where there are concrete barriers on both sides or when the alignment has a small radius curve. As the maximum width allowed by Texas permit on controlled access highways is 16-ft, clear width should be no less than 18-ft in one direction. As the maximum width allowed by Texas permit without a certified route inspection is 20-ft, any clear width less than 22-ft should be mitigated. For highways other than controlled access, horizontal clearance should not be reduced to less than the existing roadway width, excluding marked shoulders, unless restrictions are posted and detours provided for loads exceeding that width.

If achieving minimum clear width is not possible, the maximum width allowed should be posted in advance of the work zone and a detour for oversize vehicles must be provided.

Lane Widths:

10-ft lane widths are permissible for freeways in straight alignments where truck off-tracking is not likely but should only be used in limited circumstances where wider lanes are not feasible.

Shoulders:

When improved shoulders are closed due to construction constraints, road users should be given ample warning. ( Section 6G.07). Periodic pullouts for refuge should be considered if the construction phasing will reasonably allow.

Clear Zone:

Where traffic patterns are shifted into an existing clear zone, it is possible that objects that were previously outside of the clear zone will increase risk to the relocated traffic (culvert headwalls, ditch inlets not rated for traffic, side slopes greater than 6:1, etc). Consideration should be given to installing temporary traffic barrier if these hazards cannot be otherwise mitigated.

Lateral Clearance and Barrier Placement:

For operational and safety reasons, a minimum of 1-ft lateral offset, 2-ft preferred, should be provided from traffic control devices, especially concrete barriers, to the edge of traveled way during all phases of construction. This becomes more important the narrower the lanes are, the higher the ADT is, or the higher the truck percentage is.

Where TCDs, especially concrete barrier, are placed downstream of an entrance ramp lacking an acceleration lane, provide as much space as practicable at the entrance ramp merge with the freeway, allowing the traffic to encroach over the striping as needed to avoid collisions.

Where concrete barrier is placed upstream of an entrance ramp, ensure that sight distance is not obstructed for traffic making the merge. Likewise, for exit traffic merging with frontage road traffic

A lane width of 9-ft may be used for short-term stationary work on low volume, low speed roadways when vehicular traffic doesn’t include longer and wider heavy commercial vehicles ( Section 6G.08).

The following should be considered when a TCP is conducted on the THFN:

At least one 12-ft lane is encouraged. Use wider outside lane than inside lane if lane widths are restricted.
Use longer than minimum lane closure and lane transition lengths.
Use solid striping to discourage weaving through significant alignment shifts.

Use portable changeable message signs (PCMS) and other warning signs far in advance of work when lane closures or significant changes occur.

Refer to TxDOT’s for considerations associated with temporary vertical clearances during construction. Discuss with the Project Manager when temporary vertical clearances may be a controlling condition for roadway geometry.

At a minimum, bridge vertical clearances above all the travelable pavement must be a minimum of 14’-6” (15’-0” preferred) during construction to provide a sufficient buffer between allowed and actual heights to avoid over-height impacts.

Any temporary vertical clearances that are less than existing vertical clearances upstream from the construction work zone should be clearly posted and a detour provided, as necessary, for vehicles that would normally have been able to safely pass under the pre-existing structures. It is also recommended that either an automated height measurement sensor or a physical clearance bar should be installed to alert operators of any vehicles who fail to take the detour that they are over the temporary height limit.