Section 5: Freeway Signing Policies
Anchor: #i1002431Retroreflective Sheeting for Freeway Signs
In 2003, TxDOT changed the policy for retroreflective sheeting on freeway signs. The following table describes the types of retroreflective sheeting that should be used on freeway signs.
|
Sign Mounting Type |
Legend |
Background |
|---|---|---|
|
Overhead |
TxDOT Type D (microprismatic) |
TxDOT Type D (microprismatic) |
|
Ground Mounted |
TxDOT Type D sheeting (microprismatic) |
Type C Encapsulated Beaded |
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Freeway Sign Illumination
TxDOT policy is to not use overhead sign lighting unless a sign is positioned in a manner such that vehicle headlamps will not provide sufficient illumination to meet driver luminance needs. Appendix A provides a procedure to determine if sign lighting is needed.
Anchor: #i1002455Vertical Sign Clearance
There are two issues to consider for vertical signing: the clearance for overhead structures and the vertical clearance for overhead sign supports.
Overhead Bridge Structures. For information on how to measure and sign vertical clearances for overhead bridge structures, see the Signs and Marking Volume of the Traffic Operations Manual, Chapter 6, Section 3.
Overhead Sign Supports. Regarding overhead sign supports, the following is from the Texas MUTCD, Section 2A.18:
Overhead signs shall provide a vertical clearance of not less than 17 ft 6 in to the sign, light fixture, or sign bridge, over the entire width of the pavement and shoulders except where a lesser vertical clearance is used for the design of other structures. The vertical clearance to overhead sign structures or supports shall not be greater than 1 ft in excess of the minimum clearance of other structures.
In special cases it may be necessary to reduce the clearance to overhead signs because of substandard dimensions in tunnels and other major structures such as double-deck bridges.
Overhead sign structures are not required to have clearance signing, even if the minimum clearance is less than 20 ft (see the Signs and Marking Volume of the Traffic Operations Manual, Chapter 6, Section 3).
Anchor: #i1002493Control Cities
Control cities are key cities located on a freeway route that are used for destinations in freeway interchange signing and in distance signing.
The following table lists the control cities for interstate highways located within Texas. The control cities are identified in Part III — “List of Control Cities for Use in Guide Signs on Interstate Highways,” GSGLC-4 (American Association of State Highway and Transportation Officials, Washington, D.C., 20001). Control cities should be used for all interstate highways. Non-interstate freeways should use the interstate control cities where possible and should use cities of similar population or significance where it is not possible to use the interstate control cities. Any given route should have the same control cities in both directions of travel and the control cities must lie on the intersected route. Additional guidelines for destination names are included in Part 2E of the Texas MUTCD.
|
Interstate Highway Number |
Control Cities in Texas (east to west or south to north) |
|---|---|
|
10 |
Las Cruces, El Paso, Van Horn, San Antonio, Houston, Beaumont, Lake Charles |
|
20 |
El Paso, Abilene, Fort Worth or Dallas (signed alternatively), Shreveport |
|
27 |
Lubbock, Amarillo |
|
30 |
Fort Worth or Dallas (signed alternatively), Texarkana, Little Rock |
|
35 |
Laredo, San Antonio, Austin, Waco, Dallas or Fort Worth (signed alternatively), Oklahoma City |
|
37 |
Corpus Christi, San Antonio |
|
40 |
Tucumcari, Amarillo, Oklahoma City |
|
44 |
Wichita Falls, Lawton |
|
45 |
Galveston, Houston, Dallas |
|
NOTE: For Interstates that cross the state border, the list includes the first control city in the adjacent state. |
|
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Sign Support Structures
TxDOT traffic engineering standard sheets include numerous standard sheets for the design of overhead sign structures and the infrastructure related to the overhead structures (such as foundations, lighting, walkways, etc.). The standard sheets may be downloaded from the TxDOT web site at: http://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/toc.htm.