Texas is a big place.  It's nearly 880 miles from the Louisiana border near Orange to the New Mexico border near El Paso, and nearly 500 miles from the Oklahoma border north of Dallas to the Mexican border in Laredo.  That size gives the state a tremendous amount of diversity.  A hot, humid sub-tropical climate in the Valley yields to a varying Midwest climate, complete with snow, in Amarillo.  There are Piney Woods in East Texas, desert in West Texas, and plains, prairies, and the Hill Country in between.  The state has some of the nation's biggest metropolitan areas and some of its most desolate ranges.  With this size and diversity, a large and rapidly growing population, a booming economy, an increasing role in international trade, and its overwhelming dependence on the automobile, Texas cannot help but have the nation's biggest, most well-developed highway system with nearly 80,000 miles of state-maintained roads.

This primer is designed to give you an overview of the state's highway system and its idiosyncrasies.  If you're looking for a route log, check out Texas Highway Routes by David Stanek, a complete listing of all highways in Texas.  Both Ron Jackson's TexasFreeway.com  and Andy Field's LoneStarRoads sites have lots of in-depth information on freeways and other highways statewide.

Some Texas highway facts

Highways in Texas are managed by the Texas Department of Transportation (TxDOT).  TxDOT was created in 1991 from the former State Department of Highways and Public Transportation (SDHPT).  Here are some facts about the highway system in Texas:

CENTERLINE MILES (2006)
	3,233
	12,101
	16,273
	40,988
	339
Frontage Roads	6,761
TOTAL MILEAGE	79,696

• REST AREAS: 100
• PICNIC AREAS: 665
• FIRST HIGHWAY: Started in 1918 and finished in 1920, between Falfurrias and Encino in Brooks County, along present day US 281.
• FIRST INTERSTATE: 1956, I-45 (then US 75) near Corsicana in Navarro County
• SHORTEST HIGHWAY: Loop 168 in Tenaha, Shelby County, at 391 feet (.074 miles)
• LONGEST HIGHWAY: US 83 stretches 899 miles from the Oklahoma state line near Perryton to the Mexican border near Brownsville
• HIGHEST HIGHWAY: A spur from Texas 118 at the McDonald Observatory on Mt. Locke in West Texas is 6,791 feet above sea level.
• BUSIEST HIGHWAY: US 59 in southwest Houston just west of Loop 610 carries over 330,000 vehicles daily.
• LONGEST BRIDGE: The Queen Isabella Causeway between Port Isabel and South Padre Island is 2.37 miles long.
• NUMBER OF BRIDGES: 49,829

State-maintained highways comprise 26% of the total roadway mileage in Texas, but carry 74% of all traffic.

Interstates

In addition to having the nation's largest highway system overall, Texas also has more Interstate mileage than any other state.  There are 15 different Interstates in the state:

The Dallas/Ft. Worth area has two anomalies: I-35 is split into I-35E through Dallas and I-35W through Ft. Worth, and I-345 is an unsigned extension of I-45 in downtown Dallas.  Another unsigned Interstate, I-110, connects I-10 to the Mexico border in El Paso.

Interstates in Texas were generally developed along existing US and State highways.  I-45 replaced US 75, I-35 replaced US 81, and I-40 replaced the famed US 66, to name a few.  The first Interstate contract let in Texas was for a segment of I-45 in Navarro County near Corsicana in 1956.  The last Interstate to be completed was I-27 between Lubbock and Amarillo in 1992.  In urban areas, many existing freeways were simply re-signed as Interstates.

Of the inter-urban Interstates in Texas, I-35 between San Antonio and Dallas-Ft. Worth is the busiest.  Most of I-35 operates at or above its capacity.  Every traffic counter location between San Antonio and Hillsboro reported more than 50,000 vehicles per day in 2008.  As a result, traffic delays, especially during holiday periods, are common.  Besides increases in passenger vehicles, truck traffic on I-35 and other Interstates is growing rapidly, mainly as a result of the North American Free Trade Agreement (NAFTA) and the General Agreement on Tariffs and Trade (GATT).  TxDOT reports that Interstate traffic has increased every year since 1987.  Between 1996 and 1999, passenger vehicle traffic statewide increased 12% while truck traffic increased 19%, and between 1999 and 2011 truck traffic is predicted to grow 50-70%.  In fact, Texas has the highest volume of truck traffic in the nation. 

All of I-35 between San Antonio and Georgetown is now six lanes or more, and a bypass tollway (SH 130) from Georgetown to I-10 at Seguin is about half completed.  TxDOT is also participating a $1.5 million Federal study of I-35 from Laredo to Duluth, Minnesota, which aims to provide comprehensive improvements to the corridor.  (More information on the I-35 corridor between San Antonio and Austin is available as part my San Antonio roads pages.)

Exits, entrances, and the ubiquitous frontage roads
As you drive through Texas, you may notice that exits and entrances on many of our Interstates tend to be more frequent than in other states.  This is the result of the wishes of a former and long-time director of the state highway department, Dewitt Greer.  It was his belief that, given the vastness of the state, Interstates should not just serve "interstate" traffic, but also "interregional" traffic within Texas.

Another byproduct of this philosophy is perhaps the most unique feature of the state's highway system: frontage roads.  There are almost 6,800 miles of these along freeways in Texas, more-- much more-- than any other state.  The reason for the widespread use of frontage roads in Texas again can be traced to Dewitt Greer.  He decided that it was cheaper to build frontage roads to keep access to adjacent properties than it was to purchase those access rights, which is required under state law.  This quickly became standard operating procedure at the Highway Department (and subsequently TxDOT) and nearly all of the state's freeways were built under this policy.  In June 2001, the Texas Transportation Commission considered a major policy change that would've rocked TxDOT and Texans in general to the core-- frontage roads would not be included in any new freeways unless absolutely necessary.  This was a fundamental change and caused quite a stir around the state-- enough of one that the Commission decided, after statewide hearings, to scrap the idea.

There are several ramp configurations used with frontage roads.  The "diamond" interchange is pretty standard, with the on- and off-ramps connecting to the frontage roads in the general shape of a diamond relative to the cross street (see illustration below).  Sometimes, especially in urban areas, the ramps are reversed in an "X"-interchange with the exit ramp for the next cross street preceding the entrance ramp from the previous cross street.  This allows traffic to weave on the frontage road rather than the freeway.  Occasionally, if space is limited, both the on and off ramps are built at the same location in a "braided" arrangement (i.e. one ramp passes-over the other).

Frontage roads with diamond interchanges

Frontage roads with "X" interchanges

Speed limits on frontage roads generally range from 50-60 mph in rural areas to 40-50 mph in urban areas.  In urban areas, access roads are one-way in the same direction as the adjacent freeway lanes.  In rural areas they are generally two-way.  On the frontage road, traffic leaving or entering the freeway has the right-of-way.  Yield signs are usually posted, but in many areas they're lacking.  Many drivers don't realize that even if there's no sign, they're still required to yield.

Our ubiquitous frontage roads are an oddity unique to Texas.  However, within Texas, frontage roads have their own oddity.  If you travel through the state, you may notice that people in each of the major cities call their frontage roads something different: in Houston, they're "feeder" roads; in Dallas-Ft. Worth, they're "service" roads; in San Antonio, they're "access" roads.  I've heard that they're known as "gateways" in El Paso.  The term used in Austin and the state's official term is "frontage" road, which is how you'll see them marked on guide signs statewide, even in the aforementioned areas where the popular semantics differ.  You can often tell what part of the state someone hails from just by asking them what they call that road next to the freeway.

It should be noted that frontage roads (or whatever you call them) are not just found on
Interstates-- the freeway segments of many US and state highways also feature frontage roads.

Texans are frequently surprised when they go to other places and find no frontage roads.  I often hear people talk about their trips to (fill-in-the-blank) and one topic that often comes-up is, "They don't have frontage roads on their highways!"  Most native Texans don't realize how much of an oddity our extensive frontage roads are.  Conversely, many out-of-state visitors immediately notice and comment on our frontage roads.  It's usually about 50-50 between thumbs-up and thumbs-down.

Going hand-in-hand with frontage roads are "turnarounds".  These are separate U-turn ramps that allow traffic heading in one direction on a one-way frontage road to "turnaround" and head the other way on the opposite frontage road without having to traverse the two frontage road/cross street intersections (see diagram below).  This greatly eases congestion in the intersections.  Turnarounds can run below the freeway using the same underpass as the cross street, or they can cross over the freeway on the same overpass as the intersecting street or on separate overpasses.  Turnarounds are generally found only in urban areas.  Like frontage roads, these may have different names in different parts of the state.  "Turnaround" is the term in San Antonio, and it's the only place that actually uses "Turnaround" signs, although the "U-turn ONLY" sign found in most of the rest of the state is starting to make an appearance there.  Other terms used for turnarounds are "U-turn lane" and "crossover", although the later more correctly describes an opening in the median on a divided highway.

Turnaround diagram

Typical turnaround in San Antonio

"IH"
Another semantic idiosyncrasy is how TxDOT abbreviates "Interstate".  In most other states, it's
I-35, I-10, etc.  Here, TxDOT's official term is "IH", as in IH-35 or IH-10.  Of course, "IH" is short for "Interstate Highway".  Furthermore, depending which part of the state you're in, you may find lots of people on the street using it, too.  (As you can tell by my pages, I prefer "I" myself.)  I guess TxDOT likes "IH" because all of their other highway abbreviations are two letters as well.

Interstate 69
With the growth of NAFTA traffic, Texas began making plans for a new Interstate, I-69, between Texarkana and Laredo, and "Future I-69" signs began appearing on US 59 in the Houston area in 2000.  I-69 would replace the existing US 59, one of several corridors being strained by burgeoning NAFTA traffic.  As originally envisioned, one or two spur routes would connect this route to the Lower Rio Grande Valley (Brownsville-McAllen-Edinburg area).  During the first decade of this century, planning for this route was rolled-into the Trans-Texas Corridor as "TTC-69" (more details on the TTC below.)

Interstate 27 extension
TxDOT commissioned a study during the early '90s to investigate extending I-27 south from Lubbock.  Three corridors were considered: US 87/SH 349 to Midland, a Sweetwater-San Angelo-Junction corridor connecting to I-10, and another corridor through Big Spring to I-10 at Ozona.  The I-20 to I-10 segments of these corridors were studied separately.  The study concluded that there was not enough traffic, present or projected, to warrant an extension of the Interstate for the foreseeable future.  Instead, a package of upgrades to US 385, SH 349, US 87, and US 84 was recommended.

With the passage of NAFTA, additional studies have been done on this "Ports-to-Plains" corridor.  You can read more about it at Andy Field's AARoads website and at the Ports-to-Plains coalition website.  Once again, projected traffic volumes were determined to not be sufficient for an Interstate in this corridor.  Instead, various options including bypasses, intersection improvements, additional lanes on existing roads, and ITS measures were recommended.

Exit numbers
Texas, like most states, switched from a sequential exit numbering system to a milepost numbering system in the mid to late '70s and early '80s.

State highways

The State Highway system includes State Highways (SH), Loops (LP), and Spurs (SP).  There are also Park Roads and Business Routes.  There are a few "special" state highway designations as well: OSR (Old San Antonio Road) near Bryan, NASA Road 1 leading to the Johnson Space Center, and Beltway 8 around Houston.

"Loop"
A term you are sure to hear across the state is "Loop".  Even when they're Interstates, you'll usually hear beltways and other bypasses referred to as "Loop" such-and-such.  For example,
I-410 around San Antonio is usually called "Loop 410", and I-610 in Houston is known simply as "The Loop" (usually with the location inserted, e.g. "the West Loop.")  However, there is an official state highway designation of "Loop (LP)".  This category includes many routes that are not circular or even a bypass!  Short state highways whose main purpose is to connect two or more highways are usually designated as a Loop.  A good example is Loop 1 (MoPac Expressway) in Austin.  It is basically straight and runs pretty much through the heart of the city, but it connects several US, SH, and FM routes along the way.

Business Routes
Prior to 1991, all business routes carried an internal arbitrary State Highway Spur or Loop designation, although in most cases they were actually marked with the business route sign for the parent route from which they branched.  In 1991, those internal designations were dropped and the business route designations were made official.

How Texas marks business routes is unique.  Firstly, TxDOT typically puts a small letter at the bottom of most business route shields.  This letter indicates which branch in the series for the parent highway that particular segment is.  For example, US 90 passes through several towns.  The business route through the first town would be labeled "A", the one through the next town labeled "B", and so on, although this exact sequence isn't followed rigorously throughout the state.  Secondly, on US business routes, TxDOT often does not use the "BUS" or "BUSINESS" auxiliary plate mounted above the US route marker.  Rather, the word "BUSINESS" is included within the US shield above the number, as shown to the right.

Interstate Business Loops were fairly rare in Texas until the state decommissioned all US highways that were completely coexistent with Interstates in 1991.  Along those Interstates, the US route had previously provided the parent route for the business routes.  Those have since been replaced with Interstate Business Loops.

Park roads
The state also has about 88 Park Roads and Recreation Roads, which provide access to state and national parks and other designated recreational areas.  TxDOT also maintains all roads within state parks, though they are not marked state routes.

Farm-to-market roads

More than half of the state's highway system is comprised of the Farm-to-Market (FM) road system, which also includes Ranch-to-Market (RM) roads.  Although the first FM road opened in 1937, the system really grew after the 1949 Legislature set aside $15 million annually from the state's General Fund for their construction.  General Fund money is no longer used, but the FM system is still paid for entirely by the state.  The FM system is the most extensively developed rural highway system in the nation.  Its nearly 41,000 miles is more than double the entire state highway mileage of the six New England states combined.

Although the FM/RM route sign reads "Farm Road" or "Ranch Road", the routes are officially designated as "farm-to-market" or "ranch-to-market".  Larger guide signs do mark the routes as "FM" and "RM" (see the "signs" topic below.)  There is only one route officially designated as "Ranch Road", that being Ranch Road 1 leading up to the LBJ ranch east of Fredericksburg.  There is no difference between FM and RM roads; just another Texas highway idiosyncrasy.  Routes east of US 281 are generally labeled as FM roads; those west of US 281 are generally marked as RM roads. 

With the explosive growth of metropolitan areas in Texas over the years, many FM routes are now in metropolitan areas.  Houston and San Antonio in particular have a large number of FM roads within their urban areas.  One could drive many of these routes and never see a farm or ranch, much less anything being transported to market.  Still, only about 4% of the total FM mileage is within urban areas.  Since the FM system is entirely state-funded, an effort was started in 1995 to create a new classification for FM routes in urban areas called "Urban Roads" to enable them to receive federal funding.  The proposed sign would be the simple state highway square with the word "urban" and the route number.  An outcry from the public about the changing the familiar Texas-shaped sign stopped the plan to re-sign the roads, but TxDOT's internal highway designation files were changed to re-classify FM roads in metro areas as Urban Roads.

Innovation

Texas has always been on the leading edge of highway technology.  The Texas Transportation Institute (TTI) at Texas A&M University has spearheaded much of this highway research.  Here are some of the many innovations to come from Texas:

• The "Texas Twist" guardrail end was designed to deflect vehicles by burying the ends of the guardrails.  As cars got smaller, though, many flipped when hitting this.  So in the late '80s and early '90s, TTI developed a new guardrail end treatment called the ET2000.  This new guardrail end absorbs the impact of a vehicle by extruding the rail and breaking the wooden posts.
   
• Texas initiated the concept of roadside parks.  The first picnic area opened in 1930.
   
• The "Adopt-a-highway" project was developed in Texas and we were the first state to implement it statewide.  More than 45 other states have emulated this program.  There are currently about 3,800 groups collecting litter along 8,000 miles of highway.  It is estimated that this program saves the state $2.5 million a year.
   
• Breakaway sign posts and streetlights were developed in a two-year program to reduce the seriousness of roadside object impact accidents.  After 125 crashes resulted in not one single injury, the federal government mandated their use on all federally-funded roads.  Texas also  developed the breakaway "coathanger" rural mailbox support, which was recently redesigned.
   
• A modified version of the Jersey-barrier designed to reduce the likelihood of smaller vehicles flipping over on impact was developed by TTI.  TTI also designed a special heavy-duty extra-tall guardrail for a downtown San Antonio freeway ramp to prevent heavy trucks from crashing down onto a high school football field.  To test it, they crashed a fully-loaded tanker truck into it!  This rail design has since been used in many other locales where extra strength crash-barriers are needed.

Don't Mess With Texas™

During the mid '80s, the forerunner of TxDOT introduced what would become an incredibly popular anti-litter campaign.  "Don't Mess With Texas" signs went up around the state.  The slogan took off, and now you can get "Don't Mess With Texas" T-shirts, mugs, stickers, keychains, hats... you get the idea.  There have also been numerous "Don't Mess With Texas" commercials which have featured various celebrities.  In 2005, TxDOT began cracking-down on unauthorized use of the slogan and logo. 

ITS

With freeways in many areas reaching their maximum width, the Texas Transportation Commission in 1989 committed to building Intelligent Transportation Systems (ITS) in the state's largest metro areas.  The first system to go online was TransGuide in San Antonio, which at the time was the first advanced metro freeway ITS system in the nation.  TransStar in Houston followed shortly thereafter.  Most of the state's largest metro areas now have ITS systems.  These systems use technology to monitor traffic conditions and warn drivers of problems.

Signs

Texas has more road signs than any other state. There are over 500,000 signs on state maintained highways.

Texas is probably the only state that has two different versions of our highway markers.  One version is the freestanding sign, and the other is for use on freeway guide signs.  Here are some examples:

STANDALONE SHIELDS		GUIDE SIGN SHIELDS

	After World War II, the route marker for state highways was changed to today's boring square. Prior to then, the shield featured a circle with a five-point star.

Tolls roads

Until the early 2000s, Texas law prevented the state from building or operating toll highways.  Instead, they could be built and operated by subsidiaries of TxDOT or independent agencies created specifically for that purpose.  For instance, the Texas Turnpike Authority built and operated tollways in the Dallas area, including the Dallas-Ft. Worth Turnpike, which was the state's first toll road.  North Texas tollways are now operated by North Texas Tollway Authority and the Harris County Toll Authority built and operates several tollways in the Houston area (see sidebar below).  In the late '90s, a private toll road, the Camino Columbia, was built to connect the Columbia Solidarity Bridge northwest of Laredo to I-35.  (That road eventually was sold to the state and is now operated by TxDOT.)  In recent years, with worsening congestion and insufficient funding, the state has been pushing toll roads as a viable option to get new roads built.  Despite the ensuing controversy, several toll roads have recently opened in the Austin area as well as one near Tyler, and there are more toll roads planned or under construction across the state, including new tollways in the Houston, Dallas, and San Antonio area (see my San Antonio Area Tollway System page for more info), not to mention the once-proposed statewide Trans-Texas Corridor project (see below).

Trans-Texas Corridor

In 2002, Governor Rick Perry announced a concept for a massive new transportation system in Texas.  The plan, called the "Trans-Texas Corridor" (TTC), was subsequently approved by the legislature and called for 4,000 miles of superhighway/rail/utility corridors crisscrossing the state.  As envisioned, each corridor would have been 1,200 feet wide and included separate roadways for passenger vehicles and trucks, separate tracks for freight and passenger rail, and a right-of-way for utilities such as gas, oil, and water pipelines and electrical transmission and telecommunications lines.  Specifically, here's how a typical corridor would have been be divvied up:

• Four truck lanes, four each way (A on the diagram below)
• Six passenger vehicle lanes, three each way (B)
• Two sets of tracks for high-speed passenger rail, with stations (C)
• Two sets of tracks for freight rail (D)
• Two sets of tracks for commuter rail, with stations (E)
• A utility corridor about 200 feet wide (F)
• Maintenance, safety, and expansion zones as necessary

Trans-Texas Corridor typical cross-section
(Letters correspond to descriptions above)

The roadways would have had limited interchanges, with exits only at intersections with other TTC routes, Interstates, US, and major state and FM highways.  It was planned that the passenger roadways would have speed limits of 80mph.  The corridors would have been developed and operated by private companies under a state franchise.  These companies would charge tolls and fees for users. 

There were four priority corridors:

• TTC-35, to parallel or overlap I-35 from Denison to Laredo
• TTC-69/future I-69, from Texarkana to Laredo via Houston, with branches to the Lower Rio Grande Valley
• I-45 from Dallas to Houston
• I-10 from El Paso to Orange

The project, however, met with fierce opposition, especially in rural areas as the wide corridors that would be needed would have taken many acres of farming and ranch lands.  Furthermore, there was a general discontent with the concept of having the roads operated by private companies, especially ones with foreign ties.  As a result, the project was killed by the Legislature in 2009.  The TTC-35 and TTC-69 projects, which were in advanced planning at the time, continued but not under the TTC brand.  The TTC-35 project was also eventually canceled, but planning for TTC-69 (the I-69 extension) continues.

Tunnels & ferries

TxDOT operates two ferry services.  The longest is on SH 87 from northern Galveston to Port Bolivar.  Another short ferry connects Port Aransas and Aransas Pass on SH 361.  The Harris County Toll Authority studied a possible bridge to replace the Galveston-Bolivar ferry, but determined it to not be feasible.  Harris County also operates the Lynchburg Ferry east of Houston near San Jacinto State Park.

There are currently no tunnels on the state highway system.  At one time, TxDOT did operate a tunnel under the Houston Ship Channel on SH 146 between La Porte and Baytown.  It was replaced in the early '90s by the impressive cable-stayed Hartman Bridge. There are, however, three road tunnels in Texas that are not part of the state highway system-- the Washburn Tunnel, which is also under the Houston Ship Channel on Federal Road, the Addison Airport Tunnel in Addison, and one in Big Bend National Park.

Other sites of interest

	Texas Department of Transportation http://www.txdot.gov
	TxDOT - Keep Texas Moving http://www.keeptexasmoving.com/
	CorridorWatch.org http://www.corridorwatch.org
	Don't Mess With Texas campaign http://www.dontmesswithtexas.org
	Texas Highway Routes (by David Stanek) http://www.wyvern.org/mirrors/txhwys/txhwys.html
	TexasFreeway.com (by Ron Jackson) http://www.texasfreeway.com
	LoneStarRoads.com (by Andy Field) http://www.lonestarroads.com
	Port-to-Plains Coalition http://www.portstoplains.com/
	San Antonio Freeway Systems http://www.texashighwayman.com/sanantonio
	Houston Freeways http://www.houstonfreeways.com
	Dallas-Ft. Worth Freeways http://www.dfwfreeways.info