Researchers
Eric Meyer
About the research
The three models of self-illuminating vests were compared to a standard KDOT safety vest and a low-end off the shelf vest with respect to their nighttime visibility. The vests were mounted at an appropriate height for an average size worker, and a test vehicle was specially equipped to all accurate measurement of the orientation of the headlights relative to the vests. A digital video camera was used to record the vests from the drivers perspective at several vehicle orientations and distances, using both high beams, low beams, and without headlights. Custom software was developed to calculate visibility indices for each of the vests for each of the observed conditions. It was found that when the headlights were oriented directly at the vests, the self-illumination had little, if any, effect. Reflected light drowned out the self-illuminations. At eccentricities of 10 degrees, more than 20% of the vest brightness was due to the self illumination, and at eccentricities greater than 30 degrees, nearly all of the vest brightness was self-generated. The self-illuminating vests were more visible than the purely reflective vests under all conditions. In addition to the greater brightness, the blinking of the LEDs would presumably increase the vest conspicuity over a simply reflective vest, although this test did not measure conspicuity per se. The batter life was tested, and battery replacement costs would be negligible. The vests themselves are durable, but some care should be observed in storage not to damage the wires connecting the LEDs to the battery pack. The weight of the batteries was noticeable, but not egregious.
Vendor: Illumination Polymer Tech.
Researchers
Eric Meyer
About the research
The reflectorized sleeves are designed to wrap around a standard reflectorized drum, providing an alternate color scheme (orange, white, and green stripes). The use in this evaluation was to apply the sleeves to drums on an exit within an Interstate work zone where the exit is delineated by drums. The intent of the application was to provide more positive guidance for the driver by more clearly defining which two drums on the mainline mark the mouth of the exit ramp. Three configurations of sleeves were compared to baseline data collected without the sleeves. The measure of effectiveness was the speed reductions occurring within the exiting stream before the vehicles leave the mainline. Speeds were monitored just upstream of the exit and immediately downstream of the exit on both the ramp and on the mainline. Custom software was developed to identify exiting vehicles in the downstream data and extract their speeds from the upstream data. The idea is that drivers often slow while still on the mainline, partly because the ramp is more difficult to identify when delineated by drums than under normal conditions. If the drum sleeves improve the delineation of the ramp, drivers will be less apt to slow down before exiting, thus providing for smoother flow on the mainline. The sleeves were easily installed, did not come off the drums even under severe duress (i.e., being blown over by a store and being run over by a truck), and they proved to be quite durable. Several drums were hit by vehicles during the test and only one sleeve suffered major damage. The speed data showed no statistically significant difference between the baseline and any of the three tested configurations. In retrospect, the site was less than ideal for this test because the location was nearly ideal for safety. The road was flat and straight, and only a short portion of the mainline was delineated by drums. Consequently, the ramp was very well delineated without the sleeves. While the may have some benefit, they were not needed at this site. Additionally, their effect would likely be most pronounced at night when delineation is most critical, but the traffic volumes on the exit at night were too low to support statistical analysis.
Vendor: Reflexite
Researchers
Eric Meyer
About the research
The MwSWZDI has evaluated radar actuated speed displays in several contexts. One of the most significant criticisms of previous evaluations has been that data were only collected for a relatively short time period (e.g., one week or less). Popular thought is that the displays are effective for only a few days, after which the novelty effect dissipates and drivers begin to ignore the device. This evaluation was conducted on a two-lane rural commuter route just west of Lawrence, Kansas. Data were collected for approximately one hour each work day for approximately 8 weeks. The speed display was present for five weeks, with one and a half weeks of before data and one and a half weeks of after data. The data showed statistically significant reductions in mean speed, 85th percentile speed, and percent speeding. Mean and 85th percentile speed reductions were both about 5 mph. Percent speeding dropped from about 80% (baseline) to about 40% when the display was present. The percent of drivers traveling at least 5 mph over the speed limit dropped from about 30% to less than 5%. The reductions were consistent for the entire deployment, demonstrating that the speed displays effectiveness was not due to its novelty.
Vendor: Speed Measurement Labs
Researchers
Eric Meyer
About the research
The system evaluated comprised 5 VMS, 4 RTMS, 2 microwave traffic sensors, and a laptop-based system control center, all integrated via UHF radio system. The system monitors traffic at each VMS and dynamically changes the messages displayed on the VMS and the operational mode of the system based on traffic conditions downstream of each respective VMS. Three operational modes were defined: early merge, late merge, and incident. Modes were characterized by traffic speeds. Threshold speeds where the system transitioned from one mode to another were based on prior research combined with site characteristics. The test site was an approach to a freeway to freeway interchange reconstruction in Kansas City. When the system was in late merge operation, lane distributions were statistically different than when in early merge operation, but the difference was small. An entrance ramp near the merge appeared to have a very strong effect on driver lane choice, influencing drivers to merge left, even when the system instructed them to hold their lanes. The system performed well (i.e., with few technical difficulties). The results underscored the importance of considering site characteristics very carefully when selecting sites for deployment of dynamic systems and/or late merge systems, and when designing the system deployment configuration.
Vendor: Scientex Corp.
Researchers
Eric Meyer
About the research
The goal of this work was to develop a design for a portable rumble strip given the following criteria: the strip must be deployable without adhesives or fasteners; the strip must stay in place under traffic traveling at highway speeds; the strip must be deployable by two workers; and the strip must be transportable in a standard pickup bed.
Aerodynamic analyses were conducted using a low speed wind tunnel and computational fluid dynamics (CFD) modeling to map the pressures occurring in the wake of a tractor trailer traveling at highway speeds. Vehicle modeling was used to examine the interaction between vehicle tires and a strip. Prototyptes were fabricated and tested.
During testing, vehicle speed was measured with a laser gun, sound in the cabin was measured and recorded using a PC-based system, and the motion of the rumble strip during traversal was recorded using a high-speed video camera. The prototype strips were also outfitted with two accelerometers to measure the motion of the strip. The design was appropriately modified based on the test results and subsequent analyses.
The results support the premise that a strip can be fabricated that will not lift, slide, or tip under traffic. A fourth type of motion was identified during the testing, strip bound, that precipitated a significant in the design, but which could not be more thoroughly studied within the scope of this project. The design was modified to help minimize the effects of bounce, and the final Phase 1 design will be prototyped and tested during Phase 2 of this work.
Researchers
Eric Meyer
About the research
In 2003, the states involved in the Midwest Smart Work Zone Deployment Initiative identified portable rumble strips (i.e., rumble strips that require no adhesive or fasteners, making them applicable for very short term work zones) as a high priority and solicited vendors for products to be evaluated by the study. Recognizing that no existing product strictly met the requirements cited in the solicitation, this research was proposed to develop a design for such a device based on aerodynamic and static exploration. The work began with wind tunnel and computational fluid dynamics (CDF) analyses to identify and estimate the critical forces acting on the roadway in the wake of a tractor-trailer. Vehicle simulation packages were used to examine the horizontal (i.e., sliding) force applied to the device by vehicle tires. Prototypes were developed and tested using a sound meter to monitor the sound levels inside the vehicle and both accelerometers mounted to a prototype strip and a high-speed video camera to monitor the interaction between the tires and the strips and to record the strips response to the impact during traversal.
Based on the analyses conducted in this work, a strip can be constructed that will resist the lifting forces in a truck wake, will not slide down the pavement, and will resist tipping even during heavy braking. Some bounce is inevitable. A segmented design was adopted to help minimize the effects of bounce, and a prototype was fabricated and tested to examine the performance.
In order for the strip to resist the lifting forces and the tipping forces, it must be fabricated from solid steel (or something with an equal or greater specific gravity), and needs to be at least 1 ft high in order to avoid requiring excessive widths. A 1.25 in. height is recommended, yielding a recommended breadth of 4 to 6 in. A 4 in. breadth prototype and a 6 in. breadth prototype were fabricated and tested with a loaded tractor trailer at 60 mph. Significant bounce was observed, but only in those elements struck by the tires. The adjacent elements did not move, resulting in no net translation of the strip as a whole. No tipping, sliding, or lifting due to negative pressures in the truck wake were observed.
Based on these results, the design developed in this study is a feasible solution for the need for portable rumble strips.
Researchers
Eric Meyer
About the research
The ATM product is similar to that evaluated previously by the smart Work Zone Deployment Initiative (1999, 2002) from the same manufacturer. These strips were approximately 300 mil thick and 4 inches wide (they are cut to length). The adhesive is factory applied with a protective backing that is removed immediately prior to application. Previous studies have found the strips at this thickness to generate in-vehicle noise and vibration levels similar to those produced by traditional raised asphalt rumble strips (i.e., in Kansas). The strips have been demonstrated to be durable both in terms of strip wear and adhesive longevity. This study was aimed at examining the reuse of the strips facilitated by the application of a supplemental adhesive layer following each installation and removal. A test was devised to provide a relative measure of the adhesives ability to resist vertical loading. The baseline for the tests was the strip with only the factory applied layer of adhesive, which has been demonstrated to perform satisfactorily. The second point of observation was the amount of effort required for repeated installation and removal. The application of supplemental layers of adhesive was found to significantly increase the strips resistance to vertical loading, suggesting that a reapplied strip would perform at least as well as those observed in earlier work. The strips were also significantly more difficult to remove, although after the second layer of supplemental adhesive was applied, the strips could still be removed by hand by a single person, although some workers may not be able to do so. The supplemental adhesive was easily applied, and the reinstallation of the strip was comparable in effort to the initial installation. Based on the results of this and previous studies, these strips can be recommended for reuse using supplemental adhesive as per manufacturer recommendations.
The product from RTI conformed to acceptable dimensions as recommended in previous work done by the Smart Work Zone Deployment Initiative. The application and reapplication of the strips as portable rumble strips was considered with respect to the adhesion using the vendor supplied methods and the removal and reinstallation effort required. Of several adhesives provided by the manufacturer, none were deemed appropriate for the application of temporary rumble strips. The strip alone is not heavy enough to remain in place without adhesives under traffic traveling at highway speeds. Consequently, the strips as tested cannot be recommended for use as temporary rumble strips. It should be emphasized that the reason the strips cannot be recommended for this application is that the adhesives were not appropriate. The strips themselves would likely perform satisfactorily in a longer term context with the vendor supplied adhesives or in a temporary context if another more appropriate adhesive could be identified.
Vendors: Advanced Traffic Markings and RTI
Researchers
Eric Meyer
About the research
The strips were deployed in advance of a bridge repair project in central Kansas on a two-lane rural road. The construction traffic control utilized a temporary signal to control flow through the single open lane across the bridge, and standard KDOT traffic control was used in advance of the signal, including two sets of asphalt rumble strips, one starting at about 1000-ft in advance of the signal and the other at about 1500-ft. The removable strips were installed 2500-ft in advance of the signal. The thickness of the strips (roughly 1/8-in) was not sufficient to be reliably detected by drivers. However, there was a statistically significant reduction in vehicle speeds after the installation of the strips, suggesting that the orange color of the strips acted as a warning device.
Vendor: Advanced Traffic Markings
Researchers
Eric Meyer
About the research
The Safety Warning System (SWS) takes advantage of the capability of modern radar detectors to decipher a message encoded in a broadcast radar stream and display and/or announce it to the driver. Triggering a drivers radar detector focuses driver attention on the driving task, while the message provides important information, such as work zone ahead: right lane closed. If it can be assumed that radar detectors tend to be used by drivers who choose speeds well above average for the entire driving population, then the SWS also has the advantage of targeting only the fastest drivers, potentially reducing speed variation among drivers. In this test, the SWS did not result in any statistically significant changes in traffic speed characteristics. It is expected that the system would affect driver behavior, but that the installed base is too small for the changes to be detected in traffic stream at large.
Vendor: MPH Industries
Researchers
Eric Meyer
About the research
The CB Wizard was deployed on a sub-urban Interstate north of Wichita, in advance of a lane closure. Lane distribution data were collected at several distances from the taper to determine if vehicles changed lanes earlier due to hearing the warning message broadcast by the CB Wizard. System deployment and use was quick and easy. No changes were observed in lane distributions, so the effectiveness of the device could not be statistically verified.
Vendor: Highway Technologies, Inc.