Andrew Russ

Evaluation of microwave radar trailers for nonintrusive traffic measurements

A trailer using two Wavetronix microwave radar units in side-fire mode was developed to measure traffic nonintrusively, including timestamped arrival records, moving average speed (N = 16), length, and classification (0 to 20 ft, 20 to 40 ft, more than 40 ft) of each vehicle. This paper reports on an initial validation of a prototype trailer on a fourlane section of US-50 east of Athens, Ohio. Traffic on the road was independently measured with video and radar, and the results were compared with records from the trailer to verify that the trailer was measuring the traffic with reasonable accuracy. The system records the arrival of more than 95% of all vehicles, with phantom and missed counts held to less than 5% in nearly all test cases. The overall average speed based on a 90-min time period is within 3 mph of the actual overall average values, although the observed standard deviation of the trailer moving average speed readings is about two to three times that of validation data, indicating that not all...

Evaluation of the accuracy of a real-time Travel Time Prediction System in a freeway construction work zone

The accuracy of the travel times displayed by the real-time Travel Time Prediction System (TIPS) in a construction work zone was investigated. The TIPS includes changeable message signs (CMSs) displaying the travel time and distance to the end of the work zone to motorists. The travel times displayed by the CMSs are computed by an intelligent traffic algorithm and travel time estimation model of the TIPS software, which takes input from strategically placed microwave radar sensors that detect the vehicle traffic on each lane of the freeway. Besides the CMSs and the radar sensors, the TIPS includes the computer and microcontroller computing the travel times, 220-MHz radios for transmitting data from the sensors to the computer and from the computer to the CMSs, and trailers with solar panels and batteries to power the radar sensors, CMSs, and radios. The evaluation included an accuracy analysis between the predicted and actual recorded travel times. Three crews driving independently of each other in the traffic stream recorded predicted and actual travel times at three CMSs to the end of the work zone for 12 h each day for three consecutive days, resulting in 119 trial runs. On the basis of the regression analysis of actual times versus predicted times, on the average the system does a reasonable job of predicting the travel times to the end of the work zone. About 88% of the actual times recorded for each sign, and for all the signs combined, were within a range of ±4 min of the predicted time. However, a few differences (actual versus predicted) as great as 18 min were observed. It is concluded that the realtime TIPS represents a definite improvement over any static non-realtime display system. It provides, in general and most of the time, useful and relatively accurate travel time predictions to the motoring public.

VIEWING GROUND-MOUNTED DIAGRAMMATIC GUIDE SIGNS BEFORE ENTRANCE RAMPS AT NIGHT: DRIVER EYE SCANNING BEHAVIOR

The driver eye scanning study is part of a larger study conducted for the Ohio Department of Transportation to evaluate the effectiveness of ground-mounted diagrammatic guide signs placed before entrance ramps at highway freeway interchanges. This nighttime study investigated driver eye scanning behavior while approaching ground-mounted diagrammatic guide signs placed before entrance ramps. Six highway-freeway interchanges were selected in the Greater Columbus, Ohio, area for placement of the diagrammatic signs in the field. Subjects were six unfamiliar drivers, between the ages of 22 to 42. Two diagrammatic signs were located at each of the six interchanges, .5 mi (805 m) and .25 mi (402 m) before the last point of the gore, where a driver can still gain access to the correct freeway entrance ramp. Driver eye scanning behavior measurements were recorded at night to determine if the presence of the diagrammatic signs elicited an excessive number of eye fixations or was visually distracting to the drivers or both. The results indicate that the diagrammatic signs are not looked at excessively often or excessively long. The average look numbers and average look duration times indicate a normal and reasonable level of information acquisition processing employed by the drivers. These values agree with those previously obtained for regular traffic signing determined in previous eye scanning studies. Ground-mounted diagrammatic signs on multilane arterials in advance of highway freeway interchanges were not demonstrated to unduly distract drivers and detrimentally affect a driver’s looking behavior.

Nighttime expert panel and photometric evaluations of unlighted overhead guide signs

A nighttime field evaluation of four different retroreflective overhead-sign sheeting combinations (ASTM D4956 beaded Type III legend on beaded Type III background, Type IX legend on beaded Type III background, Type IX legend on Type IX background, and Type VII legend on beaded Type III background) was conducted on a section of US-30 near Mansfield, Ohio. The test-material combinations were compared when lighted and unlighted (illuminated by low-beam headlights only). Twelve Ohio Department of Transportation engineers and technicians served as evaluators, riding the test loops in 2002 Dodge Caravans. The white Type IX legend on green-beaded Type III background sheeting combination received the highest evaluation scores for appearance, conspicuity, and legibility. The scores for the Type VII legend on beaded Type III background signs were only slightly lower in all three categories. The Type IX legend on Type IX background combination received slightly lower evaluation scores, and the beaded Type III legend on beaded Type III background combination received the lowest evaluation scores. The same signing material combinations were also photometrically (luminance and luminance contrast ratio) evaluated under low-beam illumination at selected approach distances from 200 to 1,000 ft (61 to 305 m) using a 1984 Peterbilt truck, a 2002 Chrysler Town and Country minivan, and a 2002 Toyota Camry sedan, both when lighted and unlighted (low beams). Unlighted overhead signs made with either the white Type VII or the Type IX legends on green-beaded Type III backgrounds provide nighttime motorists with adequate appearance, conspicuity, and legibility.

Decision Tree for Pretreatments for Winter Maintenance

This study addressed pretreatment protocol for winter maintenance of roadways using brine. Information on pretreatment was assessed from surveys of personnel in state departments of transportation and county garages in Ohio. Field durability studies of various applications of brine were conducted on portland cement concrete and asphalt concrete pavements in Ohio. Over three winter seasons, weather events and resulting pavement conditions were documented during pretreatment and during the subsequent events using visual assessment and limited road grip tester assessment. In addition, extensive laboratory studies were undertaken to supplement the field investigations. Integration of the findings resulted in a decision tree to aid in operational planning and pretreatment.

Removal, by Vegetated Biofilter, of Medium and Low Concentrations of Pollutants from Simulated Highway Runoff

The removal of pollutants by a prototype of a vegetated biofilter was investigated at medium and low concentrations. The biofilter was 4 ft (1.2 m) wide by 14 ft (4.3 m) long and was tilted at slopes of 8:1, 4:1, and 2:1. Artificial runoff, formulated with metals, native soil, and oil at medium concentration, was delivered at a rate equivalent to a simulated 2-year storm event (medium flow) at each slope; an additional experiment using a 10-year storm event (high flow) was conducted at the 2:1 slope. The flow rates at the low concentration represented 10-year storm events. During each simulated storm event, samples were obtained from the inlet, surface runoff, and underdrain and analyzed for total and dissolved metals, total suspended solids (TSS), and oil and grease. Before and after all tests, specimens were extracted from the bed and analyzed for metal content in soil, roots, and grass. Results indicated that all constituents (seven total metals and TSS) were removed at levels above 75% (event mean concentration) for medium-concentration influent. Metals above background levels were found primarily in the first half [7 ft (2.1 m)] of the bed. Oil removal was also achieved. Removals at low concentration were lower and erratic, and residual metal concentrations in the bed were near background levels. Soil particles in the influent flow, tagged with lanthanum, were neither resuspended nor measured at any significant concentration in the outlet surface flow.

Traffic-Signal Group Relamping Model

A group relamping model was developed and evaluated by using bulb-replacement records from the Ohio Department of Transportation (ODOT) District 4 as a test case for a limited sensitivity analysis. The relatively easy-to-use Excel spreadsheet computes the costs of group relamping as a function of the relamping interval. The model shows a relatively shallow minimum region at about 10 months, with a minimized annual cost of

Effectiveness of Ground-Mounted Diagrammatic Advance Guide Signs for Freeway Entrance Ramps

38,719 to ODOT District 4 for maintaining the bulbs on its 273 signalized intersections. Results will vary somewhat in other districts or states, but the software can be applied to those cases as well. One of the major tasks involved in using the model is the need to input the individual spot relamping distances, including those from the central maintenance facility to each signal and also the distances of travel to and within clusters of signalized intersections, where each cluster takes 1 day to relamp as a group. The other major difficulty is obtaining a bulb-failure curve to use as input; in this evaluation data for the GE-Real bulb were collected over a 2-year period in ODOT District 4. The intersections also need to be clustered before using the spreadsheet. The software will provide a table of overall traffic-signal maintenance cost on an annual basis as a function of the group relamping interval from 1 to 24 months, from which the group relamping interval with the minimum annual cost can be selected.

EVALUATION OF ODOT ROADWAY/WEATHER SENSOR SYSTEMS FOR SNOW AND ICE REMOVAL OPERATIONS. PART I, RWIS

This study investigated the effectiveness of ground-mounted diagrammatic signs in the context of urban multilane arterials leading to freeways. Six highway-freeway interchanges were selected in the greater Columbus, Ohio, area for installation of the diagrammatic signs in the field. The primary measure of effectiveness was the distance at which unfamiliar drivers driving in the wrong lane changed lanes. A total of 21 and 19 test drivers unfamiliar with Columbus roads were recruited for an evaluation before and after installation of the diagrammatic guide signs. This evaluation with unfamiliar test drivers showed that drivers were able to execute a needed lane change earlier when diagrammatic signs were provided. Combining all six sites and looking at the 50th (377 m before, 819 m after) and 85th percentile (203 m before, 601 m after) lane change distances, an increase by a factor of 2.2 to 3.0 between the after and before condition was observed. In addition, a panel of 13 Ohio Department of Transportation and FHWA evaluators visited the six interchange sites and provided their input and opinions on the use of diagrammatic signs. The majority of the evaluators fully embraced the idea of diagrammatic signs. It is suggested that such signs should be used on multilane arterials in advance of highway–freeway interchanges in addition to preexisting guide signs (trailblazer assemblies), in cases in which the cost of overhead span-type sign bridges cannot be economically justified and additional advance guidance information to motorists is highly desirable.