CTR Library's Research Digest -- Jan 2010

Research Digest FORWARD ALL REQUESTS TO: The University of Texas at Austin Center for Transportation Research LIBRARY 3208 Red River • Suite 115 • Austin • Texas • 78705-2650 Phones: (512) 232-3126 and (512) 232-3138 • Fax: (512) 232-3088 Email: ctrlib@uts.cc.utexas.edu

In this Issue: State DOT Reports

Table of Contents Item 1. Transit Signal Priority Systems Application and Technology Investigation (NJ-2009-001) ......... 1 Item 2. Investigation of Enforcement Techniques and Technologies to Support High-Occupancy Vehicle and High-Occupancy Toll Operations (VTRC 10-CR1) ............................................................................... 1 Item 3. Grade 300 Prestressing Strand and the Effect of Vertical Casting Position (VTRC 10-CR2) ......... 2 Item 4. Rapid Replacement of Tangier Island Bridges Including Lightweight and Durable FiberReinforced Polymer Deck Systems (VTRC 10-CR3) ................................................................................... 3 Item 5. Benefits of Using Geotextile Between Subgrade Soil and Base Course Aggregate in Low-Volume Roads in Virginia (VTRC 10-R1) ................................................................................................................. 4 Item 6. Evaluation of Truck Lane Restrictions in Virginia: Phase II (VTRC 10-R12) ................................ 5 Item 7. Evaluation of Jointed Reinforced Concrete Pavement Rehabilitation on I-64 in the Richmond and Hampton Roads Districts of Virginia (VTRC 10-R3) .................................................................................. 6

Research and Technology Implementation Office January 2010

Research Digest Item 1 Transit Signal Priority Systems Application and Technology Investigation NJ DOT NJ-2009-001 • 2009 This report describes the process and results of research to develop an evaluation process that will assist NJ Transit in quickly determining which intersections are good candidates for Transit Signal Priority (TSP). This evaluation process is applicable for passive and active TSP and could be applied to a variety of roadways, including urban arterials, state routes and county roads.

Full-text PDF of this report is available for free download from http://www.state.nj.us/transportation/refdata/research/reports/NJ-2009-001.pdf

Item 2 Investigation of Enforcement Techniques and Technologies to Support High-Occupancy Vehicle and High-Occupancy Toll Operations VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR1 • 2009 High-occupancy vehicle (HOV) facilities in Virginia have proven to be effective in enhancing mobility. This success, along with the availability of electronic toll collection technology, has led the Commonwealth to expand the HOV system and pursue the implementation of high-occupancy toll (HOT) facilities in the state. Although these facilities hold promise to help address the growing demand for travel in Virginia, a significant challenge in achieving their potential lies in the ability to enforce occupancy requirements in a manner that has minimal impact on the operation of the facilities. This has proven to be a challenge for HOV facilities and will be an even more complex undertaking on HOT facilities.

The purpose of this study was to examine occupancy enforcement on HOV and HOT facilities. This examination focused on three areas: assessing the impact of existing manual violation enforcement techniques on HOV violation rates; exploring the feasibility of using new technologies/techniques to improve the effectiveness of violation enforcement; and assessing the impact of violation enforcement techniques on the operations of HOV/HOT lanes.

The results of the research indicate that current saturation enforcement techniques are not effective in reducing violation rates. However, no proven technologies are currently available that offer the potential to automate enforcement of occupancy restrictions. Finally, a simulation methodology was developed that may be used to estimate the operations’ impacts on current and future enforcement techniques and technologies.

The report offers a number of recommendations to address the challenges of HOV/HOT occupancy enforcement in Virginia: (1) the current practice of sporadic saturation enforcement should be discontinued in exchange for regular, continuous enforcement; (2) the HOV Enforcement Task Force should look critically at current HOV policies to identify and recommend specific changes to reduce the likelihood of citations being dismissed in adjudication; and (3) the methodology developed in this research should be used to evaluate new enforcement techniques and technologies before they are implemented.

Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-cr1.pdf _____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 1

Research Digest Item 3 Grade 300 Prestressing Strand and the Effect of Vertical Casting Position VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR2 • 2009 The purpose of this investigation was (1) to compare the differences in the transfer length, development length, and flexural strength among Grade 300 strand, the traditional Grade 270 strand, and the predictions of these properties obtained using current code equations for prestressed concrete members, and (2) to determine the effect the as-cast vertical location of the strands (top-strand effect) on these properties. The current code provisions by the American Association of State Highway and Transportation Officials and the American Concrete Institute are based on years of experimental research on the traditional Grade 270 strand.

The scope of this project was limited to the fabrication and testing of 20 pretensioned, prestressed beams, 10 of which contained Grade 270 and 10 of which contained Grade 300 strands constructed and tested in the Structures and Materials Laboratory at Virginia Tech.

The increase in strand strength was found to influence transfer length, development length, and flexural strength; the ascast vertical location was found to influence only transfer length and, in turn, development length. Transfer lengths of the Grade 300 strand had an average increase of 10 percent compared to the transfer lengths of the Grade 270 strand. Development lengths for the Grade 300 strand were also shown to increase compared to the Grade 270 strand. Flexural bond lengths were found to be relatively the same for both strand strengths, indicating the increase to be primarily dependent on the increase in transfer length.

Minimum flexural bond lengths that resulted in flexural failures were found to be in the range of 45 to 50 in for both strand strengths. The influence of strand strength on flexural strength was also evaluated. As expected, members cast with ½ in diameter, Grade 300 strands had about 11 percent higher nominal moment capacities than did those cast with ½ in diameter, Grade 270 strands. Contrary to the historical definition, the topbar/strand effect was found to be more dependent on the amount of concrete cast above the strand than the amount below it, with transfer lengths showing a steady increase with a decrease in the amount of concrete cast above the strand. The current equations for flexural strength were found to give adequate estimates for flexural strength, although a decrease in ductility was noted.

The study recommends the following: 1. VDOT’s Structure and Bridge Division should use the current AASHTO equation for transfer length and development length for flexural members containing Grade 300 strand cast in non-top strand situations.

2. VDOT’s Structure and Bridge Division should use the current ACI and AASHTO provisions for the calculation of nominal moment capacity for flexural members containing Grade 300 prestressing strands, Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-cr2.pdf

_____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 2

Research Digest Item 4 Rapid Replacement of Tangier Island Bridges Including Lightweight and Durable Fiber-Reinforced Polymer Deck Systems VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR3 • 2009 Fiber-reinforced polymer (FRP) composite cellular deck systems were used as new bridge decks on two replacement bridges on Tangier Island, Virginia. The most important characteristics of this application were reduced self-weight and increased durability for an FRP deck system over a reinforced concrete bridge deck.

Tangier Island is in the Chesapeake Bay and is accessible only by water or air; each bridge is over saltwater. The two bridge deck systems used were from different manufacturers: Strongwell Corp. and Zellcomp, Inc. The deck system from Strongwell was virtually identical to a previous application by the Virginia Department of Transportation (VDOT) in Covington, Virginia. Because of the extensive testing of this system conducted as part of a prior Innovative Bridge Research and Deployment project, further investigation of its behavior was not warranted. The objectives of the testing of the Zellcomp deck system were four-fold: (1) investigate connection behavior under simulated pseudo-static service load; (2) examine flexural strength and failure mode of connections and deck; (3) explore fatigue behavior during simulated cyclic wheel loading and residual strength after fatigue loading; and (4) investigate viability of transition connection.

Two test sections were constructed in the Structures and Materials Laboratory at Virginia Tech. The test sections included sections of the Zellcomp deck attached to supporting steel stringers. The first was flat, 11 ft by 8 ft in plan, and subjected to static and simulated truck loadings. The second included a transition connection and was 17 ft by 8 ft in plan. Of special interest during this testing was the investigation of the static and cyclic behavior of all Zellcomp deck connections (topplate to supporting T-sections, T-section to T-section, and T-section to supporting stringers).

The flat Zellcomp deck test specimen had a 1.4 safety factor against sustaining permanent damage and a 2.4 safety factor against failure when subjected to an HL-93 wheel load of 22 kips. There was no measured composite action between the top plate and supporting T-section. Generally, the specimen performed well during the fatigue test. However, there was some indication of deterioration of the lap joint connections at 1 million cycles of load and loss of stiffness at about 2.5 million cycles of load. The bent lap joint connection was difficult to construct. A permanent gap between the top plate and supporting Tsections resulted because of inherent construction tolerances. The slope Zellcomp deck specimen underwent significant deterioration during the first 600,000 cycles of load. Numerous top plate screw connections loosened, with several completely fracturing.

The damage to the deck increased for the next 400,000 cycles.

The study recommended that VDOT’s Structure and Bridge Division (1) not use the sloped deck transition on any application considering its use on any bridge structure that has truck traffic. The Tangier Island Bridge is subjected to very light truck traffic, and the Zellcomp system proved to be adequate for this specific application only.

Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-cr3.pdf

_____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 3

Research Digest Item 5 Benefits of Using Geotextile Between Subgrade Soil and Base Course Aggregate in Low-Volume Roads In Virginia VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R1 • 2009 Geosynthetics have increasingly been used since the 1960s in pavement structures to provide reinforcement; to serve as a permeable separator to prevent mixing of subgrade with subbase or base course materials; and to provide drainage. A reliable method of quantifying these benefits is needed to justify the more widespread use of these materials.

The purpose of this study was to quantify the benefit of using a geotextile as a separator in low-volume roadways such as secondary and subdivision streets. A field trial was conducted on a section of Virginia Route 743 near the Charlottesville-Albemarle Airport in Albemarle County to achieve this objective. A geotextile was placed between the aggregate base and subgrade in one lane of the section to prevent failure attributable to intermixing, and the adjacent lane was left unmodified as a control. In addition to the field trial, a small-scale accelerated loading laboratory test was conducted to quantify the benefit of using geotextile as a separator for a range of pavement design variables, including variations in soil strength, traffic volume, and aggregate properties.

A statistical analysis of data gathered by a falling weight deflectometer during construction and after 8 months of traffic showed the lane with geotextile to have a slightly higher structural capacity. As severe intermixing and base failure in the control section were not expected during the 8-month period because of the low volume of traffic and a dry season, the benefit may have been attributable to a reinforcing effect.

Although the size of the apparatus and the boundary condition may have prevented the most accurate quantification of the benefit, the laboratory testing further demonstrated the benefit. Most laboratory samples with geotextile had less deformation than the control sample. Intermixing of soil and aggregate was not observed when very densely graded base aggregate was used. When a more open-graded aggregate was used, the geotextile reduced the amount of fines migration into the aggregate layer; however, the fouled aggregate did not appear to have lost significant structural stiffness. Therefore, the separator benefit of geotextile in the laboratory testing was also apparently attributable to a reinforcing effect.

The use of geotextile materials appears to have great potential to extend the service life of pavements on the secondary road system, offering significant cost savings to VDOT. It is recommended that this section of road be periodically evaluated to quantify this potential increased service and that more test sections on subdivision streets with a weaker subgrade condition or full-scale accelerated testing be conducted for a reliable quantification of the benefit.

Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r1.pdf

_____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 4

Research Digest Item 6 Evaluation of Truck Lane Restrictions in Virginia: Phase II VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R12 • 2009 Virginia, like many other states, has used truck lane restrictions on parts of its interstate system in an attempt to improve mobility and safety. The Code of Virginia currently specifies two types of lane restrictions. First, trucks may not travel in the left-most lane of interstates with three or more lanes by direction (1) when the speed limit is 65 mph or higher, (2) along all of I-81, and (3) along interstates in the Virginia Department of Transportation’s (VDOT) Northern Virginia District. Second, trucks may not travel in the left lane of two-lane directional interstate segments when their speed is below the posted speed limit; this restriction was enacted in 2007 and was intended to reduce cases of trucks impeding traffic flow on steep grades in the western part of the state.

This report describes Phase II of a 2007 study that found that the safety impact of the first type of restriction appeared to be affected by traffic volume. Safety was enhanced on low- volume roads (i.e., annual average daily traffic [AADT] less than 10,000 vehicles per day per lane [vpdpl]) but degraded on high-volume roads (i.e., AADT above 10,000 vpdpl). Given that most of the high-volume interstates investigated were in Northern Virginia, there was a need to re-examine the safety analysis to ensure that the findings were not a product of the growing congestion in the region but rather were attributable to the effects of the truck lane restrictions.

The purpose of this study was to provide a detailed assessment of the safety and mobility impacts of Virginia’s truck lane restrictions, expanding on the Phase I study. First, crashes on high-volume interstates with three or more lanes by direction noted in the Phase I study were re-examined. Individual crash reports were reviewed, and any crashes that were not influenced by the restriction were removed from subsequent analysis. An empirical Bayes analysis was then used to re-assess safety using the screened crashes. Second, the operational and safety impacts of the restriction on two-lane segments of interstate were examined. Third, the effect of an enforcement campaign on compliance with the restriction for two-lane segments was determined.

The crash analysis for the high-volume, three-lane segments confirmed that crashes were higher than expected after the restriction was put in place and thus were not merely the products of growing congestion. The safety and operational impacts of the restriction for two-lane interstates revealed no significant benefits, likely because the level of non-compliance with the restriction was high. With regard to the effect of the concentrated enforcement campaign, compliance improved, but the improvement was relatively modest.

The study recommends that VDOT (1) pursue a legislative modification to remove truck lane restrictions on high volume interstates with three or more lanes in each direction; (2) determine if signing could be modified to improve compliance; (3) partner with the Virginia State Police and the Virginia Trucking Association to increase compliance on the two-lane directional segments of interstate; and (4) direct a study to re-evaluate the effectiveness of the two-lane restrictions once at least 3 years of “after” crash data are available. Removal of the truck restrictions on the specified high-volume interstates should create crash reduction benefits. If crash costs are converted into dollars, an estimated $266,996 of crashes would be eliminated statewide annually through removal of these restrictions. Those costs accrue to drivers. Additional direct savings to VDOT would occur through the reduction of signing.

Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r12.pdf

_____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 5

Research Digest Item 7 Evaluation of Jointed Reinforced Concrete Pavement Rehabilitation on I-64 in the Richmond and Hampton Roads Districts of Virginia VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R3 • 2009 Beginning in 2004, the Virginia Department of Transportation (VDOT) undertook a series of pavement rehabilitation projects to address deficiencies in three sections of the I-64 corridor between Richmond and Newport News. I-64 serves as the primary avenue between the Richmond and Hampton Roads metropolitan areas and carries a combined traffic volume ranging from approximately 20,000 to 90,000 vehicles per day. For nearly 100 mi, this roadway is a four-lane divided facility that was originally built between the late 1960s and early 1970s as either a jointed reinforced or continuously reinforced concrete pavement. The existing concrete pavement was rehabilitated using three rehabilitation procedures: two standard approaches and an experimental approach. The standard rehabilitation procedures included the use of full-depth portland cement concrete (PCC) patches overlaid by a hot-mix asphalt (HMA) overlay and full-depth PCC patches followed by grinding of the pavement surface.

The experimental rehabilitation procedure consisted of the use of full- and partial-depth HMA patches followed by an HMA overlay. The purpose of this study was to document the initial condition and performance to date of the I-64 project and to summarize similar work performed by state departments of transportation other than VDOT. The pavement rehabilitation cost per lane-mile was nearly 20% less for the section of I-64 for which full-depth PCC patches followed by grinding of the pavement surface was used than for the other two sections. However, the experimental results do not allow for a comparison to determine any differences in the structural capacity or service life between the sections.

The study recommends that VDOT’s Materials Division annually monitor the ride quality of the pavement in the three rehabilitated sections of I-64 so that the end of service life can be defined as the pavement roughness increases because of deterioration. Further, the Virginia Transportation Research Council should collaborate with other research organizations to encourage and pursue full-scale or laboratory-scale accelerated pavement testing to determine the optimum repair materials and methods for pre-overlay repair of existing PCC pavements and to develop models to quantify the deterioration of an asphalt overlay placed over an existing concrete pavement because of reflection cracking.

Full-text PDF of this report is available for free download from http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r3.pdf

_____________________________________________________________________________________________ Research and Technology Implementation Office January 2010 Page 6