Texas Department Of Transportation Project Research Articles

Dynamic Contract Time Determination System for Highway Projects

Texas Department of Transportation (TxDOT) projects have been experiencing significant delays. Some of these delays can be rooted to the inaccurate estimation of the contract time. This research presents a preliminary framework for the development of a computer-based system designed to determine a realistic contract duration for TxDOT projects. In addition to traditional deterministic scheduling, the system also performs probabilistic scheduling using the program evaluation and review technique. The system also incorporates an interactive database containing a list of various highway construction activities and their productivity rates; the database is used to estimate the durations of project activities. The system was deployed to reschedule some previous TxDOT projects, and the results were statistically compared and analyzed. The results show that this system can significantly improve the estimate of the contract time. This framework lays the foundation for the development of a more advanced contract time determination system based on probabilistic scheduling.

Manual for Assessing Safety Hardware Crash Testing and Evaluation of Multiple Mailbox Supports for Use with Locking Architectural Mailboxes

With increasing concern about mail-identity theft, there is a growing demand among homeowners and businesses for the use of locking mailboxes for theft deterrence and resistance to vandalism. Lockable mailbox products can be significantly larger and heavier than standard lightweight mailboxes. Therefore, the Texas Department of Transportation (TxDOT) requested evaluation of their crashworthiness before permitting their use on the state highway system. Under TxDOT Project 9-1002-12, crash tests were performed following the Manual for Assessing Safety Hardware (MASH) guidelines and procedures to assess the impact performance of lockable, secure mailboxes in both single and multiple mount configurations. Testing of the larger and heavier locking mailboxes on multiple-mount support posts was unsuccessful owing to vehicle windshield deformation and intrusion. This paper describes the efforts to develop and evaluate the crashworthiness of new proposed designs for multiple mailbox supports used with a combination of lockable and standard mailboxes. The crash tests were performed following MASH guidelines and the evaluation criteria. Two proposed designs were evaluated through full-scale crash testing. Both systems satisfied all required MASH evaluation criteria at low and high impact speeds using a passenger car, which was considered to be the critical design vehicle based on the mailbox mounting height.

Eligibility Testing at Three Prehistoric Sites at Lynch Creek, Lampasas County, Texas

In August 2004, archeologists from the Cultural Resources Section of the Planning, Permitting and Licensing Practice of TRC Environmental Corporation’s Austin office conducted National Register eligibility testing and geoarcheological documentation at three previously unrecorded prehistoric sites, 41LM49, 41LM50, and 41LM51, at two separate bridge crossings over Lynch Creek (TxDOT Project CSJ: #0231-15-032; designated East and West) by Farm to Market Road 580W (FM 580W) in western Lampasas County, Texas. This archeological investigation was necessary under the requirements of Section 106 of the National Historic Preservation Act (NHPA), the implementing regulations of 36CRF Part 800 and the Antiquities Code of Texas (Texas Natural Resource Code, Title 9, Chapter 191 as amended) to assess eligibility of all three cultural resource sites for listing on the National Register of Historic Places (NRHP) and for designation as a State Antiquities Landmark (SAL). This eligibility assessment was for the Texas Department of Transportation (TxDOT), Environmental Affairs Division under a Scientific Services Contract No. 573XXSA006 (Work Authorization No. 57315SA006). The analysis and reporting were conducted under contracts 575XXSA008 (Work Authorization 57510SA008), 577XXSA003 (Work Authorization No. 57704SA003) and 571XXSA003 (Work Authorization 57113SA003). All work was performed under Texas Antiquities Committee Permit No. 3494, issued by the Texas Historical Commission (THC) prior to the planned replacement of the two bridges. The materials, artifacts, records, and photographs will be curated at Texas Archeological Research Laboratory (TARL) in Austin.

Assessing the Direct Employment Impact of Federal Economic Stimulus Funds on Construction Projects in Texas

Owing to the 2008 economic downturn in the United States, the construction industry lost 632,000 jobs nationally, of which approximately 100,000 were in Texas. In response to the economic recession, a stimulus package known as the American Recovery and Reinvestment Act (ARRA), was signed by President Obama on March 6, 2009. This paper presents the results of a study examining the construction employment impact of ARRA spending on Texas transportation projects. The primary goal of this study was to estimate direct employment in the construction industry from spending on construction projects. By using regression analysis, the study assesses employment from data on Texas Department of Transportation projects that used ARRA funds, showing that employment generated by construction projects depends on project type, size, and location urbanization. The findings can be useful to policy makers in allocating funds on construction projects when employment stimulation is an objective.

Field Evaluation of Automated Flagger Assistance Devices in Work Zones on Two-Lane Roads

Automated flagger assistance devices (AFADs) are designed to be operated remotely by a flagger positioned outside of the travel lanes and thus to reduce the flagger's exposure to vehicular traffic. There are two types of AFADs. One type uses a remote-controlled stop and slow sign to alternate the right-of-way; the other uses remote-controlled red and yellow lenses to alternate the right-of-way. A gate arm is required only with the latter. Although AFADs may have increased the safety of flaggers, there were concerns that motorists may have misunderstood AFADs and proceeded before it had been safe to do so. As part of a recent Texas Department of Transportation project, Texas A&M Transportation Institute researchers conducted field studies at lane closures on two-lane, two-way roadways in Texas to assess the operational and safety effectiveness of AFADs relative to the use of flaggers. The research findings show that the violation rate for the stop–slow AFAD without a gate arm is the highest and is significantly higher than the violation rate for the red–yellow lens AFAD (which requires a gate arm). Adding a gate arm to the stop–slow AFAD decreased the violation rate such that it was not significantly different from the red–yellow lens AFAD. In addition, alternative supplemental signs increased motorists' understanding that the stop sign would have changed to a slow sign when motorists were allowed to proceed. Overall, the research findings show that some motorists violate AFADs, especially when the queue of vehicles going in the same direction is visible to the stopped motorist.

Motorists' Understanding of Automated Flagger Assistance Devices in Work Zones

Automated flagger assistance devices (AFADs) are designed to be operated remotely by a flagger positioned outside the travel lanes and thus to reduce their exposure to vehicular traffic. There are two types of AFADs: one type uses a remote-controlled stop and slow sign to alternate the right-of-way and the other uses remote-controlled red and yellow lenses to alternate the right-of-way. A gate arm is required only with the latter. Although AFADs may have increased the safety of flaggers, there were concerns that motorists might have misunderstood AFADs and proceeded before it had been safe to do so. As part of a recent Texas Department of Transportation project, Texas A&M Transportation Institute researchers conducted surveys to assess motorists' understanding of both types of AFADs. For the stop–slow AFAD, a newly designed “Wait on Stop–Go on Slow” symbol sign resulted in the highest percentage of participants who understood that they should stop and remain stopped until the AFAD indicated that it was safe to proceed. However, for all of the stop–slow AFAD treatments, a portion of the participants indicated that they would have stopped and then proceeded instead of waiting until the AFAD displayed the slow sign. Thus researchers recommend that a gate arm be required with stop–slow AFADs. For the red–yellow lens AFAD, participants understood the stop phase. However, there was evidence of a lack of understanding of the difference between the proceed and transition phases. Even so, the use of the gate arm appeared to inform motorists when to proceed and when to stop.

Design and Performance Evaluation of Fine-Graded Permeable Friction Course

Permeable friction courses (PFCs) are popular in Texas, where the current specification for PFC (Item 342) has a maximum aggregate size of 1/2 in. and is typically placed in layer thicknesses of 1.5 to 2 in. In this study fine-graded PFCs composed of a single aggregate fraction are proposed for placement at a nominal thickness of 1 in. Initial laboratory testing found that the target air void content for volumetric design would be around 26% air voids, substantially higher than the current PFC designs, which are between 18% and 22% air voids. To minimize the likelihood of failure, extensive laboratory testing was performed to arrive at the proposed design. Tests included Hamburg wheel-track testing, overlay tester cracking, and Cantabro, draindown, and water flow tests. The proposed fine PFC mix was first placed on a test track in Pecos, Texas. Two designs were placed and subjected to limited traffic loadings, field water flow, noise, and skid measurements. These test sections performed well. The next section was placed on a Texas Department of Transportation project in May 2011 and subjected to extremely intense traffic loading conditions on an exit ramp on US-59 in Lufkin. This ramp has a high frequency of wet-weather accidents. In addition to extreme traffic loads, the surface experienced extreme heat (air temperatures approaching 105°F) and heavy localized rain (a 6-in. rain event within a 24-h period). After 3 months the fine PFC is holding up well.

Driver Performance at High Speeds Using a Simulator

The goal of a Texas Department of Transportation project was a better understanding of driver performance at high speeds. Because of limited opportunity to study high-speed driving, one of the approaches used in the study was a driving simulator. The objective of the study was to measure how long drivers took to notice and react to a lead vehicle decelerating. Conditions that varied were initial speed, lead vehicle type, lead vehicle deceleration rate, and workload level. The recorded simulator data provided the research team with the driver's actual proximity to the lead vehicle at each time increment. Findings from this study included the following: higher initial speeds were associated with statistically significant longer reaction times; reaction times when following a smaller vehicle (a car in this experiment) were longer than those when following a large vehicle (a truck); brake reaction times were shorter with faster deceleration rates; and greater headways present at the start of a deceleration event were associated with longer reaction times.

Guidelines for Spacing between Freeway Ramps

Existing geometric design guidance related to interchange ramp spacing in the Texas Roadway Design Manual and AASHTO's Policy on Geometric Design of Highways and Streets is not speed dependent even though intuition indicates that spacing and speed are related. Understanding the relationship between interchange ramp spacing, speed, and freeway operations is important, especially in developing potential design values for higher speeds (e.g., 85 to 100 mph). The objectives of this Texas Department of Transportation project were (a) to investigate relationships between weaving length, speed, and overall vehicle operations for successive ramps on Texas freeways and (b) to propose updates to current guidance on recommended distances between ramps. Several methods were used to assist in developing guidance on ramp spacing lengths. The methods and resources used to generate potential lengths included (a) guidance provided in the Design Manual for Roads and Bridges published by the Highways Agency in England, (b) minimum deceleration and acceleration lengths for freeway conditions, (c) decision sight distance, (d) sign spacing needs, (e) NCHRP Project 3–75 findings, (f) findings from field studies at seven sites in Texas, (g) findings from simulation conducted as part of this research, and (h) safety relationships identified in the literature. Suggested ramp spacings were developed for the entrance–exit and exit–exit ramp scenarios.

Application of Rolling Dynamic Deflectometer to Forensic Studies and Pavement Rehabilitation Projects

Characterization of the load transfer of jointed plain concrete pavements requires proper tools. The rolling dynamic deflectometer (RDD) has been used successfully on many Texas Department of Transportation projects for this purpose. Applications of the RDD in forensic studies and pavement rehabilitation projects are presented. RDD deflection profiles were used to assist in diagnosing the causes of reflective cracks on SH87a, where a reflective crack relief interlayer was placed in a rehabilitation project to minimize reflective cracking. However, frequent and severe reflective cracks still occurred on SH87a in the turning and inside lanes, where traffic is lighter than in the outside lane. It was concluded that poor load transfer at joints (indicated by high relative vertical movements) was one of the main contributing factors to the reflective cracking in these two lanes. Two rehabilitation projects are also presented to show how continuous RDD deflection profiles were critical to the success of the projects. In the BU287 project, RDD profiles were used to identify successfully locations for full-depth repair in Subsection 1 and recommend a different rehabilitation strategy (remove and reconstruct) in Subsection 2 because of the significant number of joints that have a severe potential for reflective cracking. In the SH87b rehabilitation project, the RDD was employed to identify locations that need dowel bar retrofit and other locations that need full-depth repair. It is concluded that RDD data not only are able to provide 100% coverage but also offer quantifiable and objective information for forensic and rehabilitation studies in terms of relative movements at joints and cracks.

Cash Flow Projections for Selected TxDoT Highway Projects

In planning for contractor payments, an owner with multiple projects needs to estimate the amount of money to be paid to contractors in coming months. For an owner as large as the Texas Department of Transportation (TxDoT), one is faced with the problem of organizing the budget to ensure that there are sufficient funds for all projects. This investigation was requested by TxDoT to provide a tool to forecast future project payments. Recent account summaries of TxDoT projects from 2001 to 2003 were analyzed for creating mathematical models representing monthly payments for various projects. The data were organized into categories of project types and subcategories of project contract amount. A fourth degree polynomial regression analysis was run on the data and the regression curve, when statistically significant, was taken to be the forecast payment curve. Finally, a computer program was developed to implement the results of the investigation for TxDoT’s needs. The methodology provided will help other highway agencies to create their own equations to better predict project cash flows and trends. This investigation might also benefit researchers in projecting cash flows and trends, while also allowing for improvements.

Using the Rural Two-Lane Highway Draft Prototype Chapter

The TRB Highway Safety Manual Task Force is providing direction and oversight in the preparation of a new document to be called the Highway Safety Manual (HSM). The complete version of the HSM is expected to be released to the public in 2007. A draft prototype chapter (DPC) for rural two-lane highways is available for review. A Texas Department of Transportation project explored the use of the DPC by applying the methodology to two case studies and exploring methods to develop calibration factors. The lessons learned from the effort can be used to improve the DPC along with other chapters in development. Additional guidance is needed on (a) how to identify segments, (b) acceptable minimum segment lengths, (c) how best to combine the predictions for intersections with those for tangents and curves, (d) the key variables within the procedures and appropriate assumptions when data for those variables are not available, (e) the confidence in the approach for individual roadway segments as opposed to a roadway...

Using the Rural Two-Lane Highway Draft Prototype Chapter

The TRB Highway Safety Manual Task Force is providing direction and oversight in the preparation of a new document to be called the Highway Safety Manual (HSM). The complete version of the HSM is expected to be released to the public in 2007. A draft prototype chapter (DPC) for rural two-lane highways is available for review. A Texas Department of Transportation project explored the use of the DPC by applying the methodology to two case studies and exploring methods to develop calibration factors. The lessons learned from the effort can be used to improve the DPC along with other chapters in development. Additional guidance is needed on ( a) how to identify segments, ( b) acceptable minimum segment lengths, ( c) how best to combine the predictions for intersections with those for tangents and curves, ( d) the key variables within the procedures and appropriate assumptions when data for those variables are not available, ( e) the confidence in the approach for individual roadway segments as opposed to a roadway, ( f) the potential of using confidence intervals in the prediction process, and ( g) how best to use the predictions generated from the methodology.