Raul Avelar

Driver Yielding at Traffic Control Signals, Pedestrian Hybrid Beacons, and Rectangular Rapid-Flashing Beacons in Texas

This research effort explored the factors associated with higher driver yielding rates at pedestrian crossings with traffic control signal (TCS), pedestrian hybrid beacon (PHB), and rectangular rapid-flashing beacon (RRFB) treatments in Texas. The percentages of drivers yielding to a staged pedestrian were collected at 7 TCS sites, 22 RRFB sites, and 32 PHB sites. Overall, TCSs in Texas had the highest driver yielding rates, with an average of 98%. The average driver yielding rate for RRFBs in Texas was 86%, whereas the average for PHBs was 89%. The RRFB results for Texas were slightly higher than those found in other studies, perhaps because all RRFB sites included in this analysis had “School Crossing” signs and were located near a school. The number of devices within a city may have an impact on driver yielding. Those cities with a greater number of a particular device (i.e., Austin, Texas, for the PHBs and Garland, Texas, for the RRFBs) had higher driver yielding rates than cities where the device was used at only a few crossings. A comparison of the number of days since installation revealed statistically significantly higher driver yielding rates for those devices that had been installed longer. For PHBs, the results support the use of PHBs on roadways with multiple lanes or a wide crossing. For RRFBs, a lower rate of compliance was observed for longer crossing distances and indicated that for a certain crossing distance width, a device other than the RRFB should be considered.

Influence of Land Use and Driveway Placement on Safety Performance of Arterial Highways

Characterizing driveway safety is a relevant and relatively complex topic in transportation safety research. This research studied the safety link of driveways abutting Oregon highways and considered various factors proposed in the current literature for design and evaluation of the safety performance of roadside elements. On the basis of two probability samples from rural and urban arterial state highways, this research developed alternative safety performance functions to evaluate the safety impacts of various driveway configurations. These safety performance functions were intended to explore driveway safety beyond the average driveway density treatment commonly encountered in the literature. The statistical models and methodologies in this research are comparable with those in the Highway Safety Manual. The proposed models exhibited different ranges of effects for urban and rural conditions, but type of land use proved a prominent factor for both the urban and the rural models. The analysis showed that roadside safety is influenced mainly by driveways associated with commercial and industrial land uses in the urban environment. Similarly, industrial driveways are more influential for safety than other types in rural environments. In addition, the rural model uncovered a safety connection to clusters of driveways rather than to driveways alone. This research indicated that after driveway land use in rural environments was accounted for, clustered driveways tended to have fewer crashes compared with isolated driveways.

Investigation on the wrong way driving crash patterns using multiple correspondence analysis

Wrong way driving (WWD) has been a constant traffic safety problem in certain types of roads. Although these crashes are not large in numbers, the outcomes are usually fatalities or severe injuries. Past studies on WWD crashes used either descriptive statistics or logistic regression to determine the impact of key contributing factors. In conventional statistics, failure to control the impact of all contributing variables on the probability of WWD crashes generates bias due to the rareness of these types of crashes. Distribution free methods, such as multiple correspondence analysis (MCA), overcome this issue, as there is no need of prior assumptions. This study used five years (2010-2014) of WWD crashes in Louisiana to determine the key associations between the contribution factors by using MCA. The findings showed that MCA helps in presenting a proximity map of the variable categories in a low dimensional plane. The outcomes of this study are sixteen significant clusters that include variable categories like determined several key factors like different locality types, roadways at dark with no lighting at night, roadways with no physical separations, roadways with higher posted speed, roadways with inadequate signage and markings, and older drivers. This study contains safety recommendations on targeted countermeasures to avoid different associated scenarios in WWD crashes. The findings will be helpful to the authorities to implement appropriate countermeasures.

Closed-Course Study of Driver Detection of Pedestrians Beyond Flashing Beacons Within Sign Assembly

This study evaluated the effect of yellow rapid flashing beacon characteristics on the ability to detect objects located behind a sign during a closed-course driving study sponsored by FHWA. For the analysis focusing on object detection distance, the results indicated that certain study assemblies were associated with shorter object detection distances. During the day, the object detection distance was shorter for objects behind an assembly with two rectangular beacons below the sign (R-B), as opposed to other beacon arrangements, such as two rectangular beacons above the sign and two circular beacons below or above the sign. At night, the detection distance to an object was shorter behind an assembly with R-B when compared with an assembly with two 12-in. circular beacons below the sign. These findings indicated that characteristics of the R-B, such as the light intensity or the location of the beacons, might negatively affect the drivers ability to see an object. For the analysis focusing on the accuracy of detecting objects, which considered the number of objects missed by the participants, the location of the beacons (above or below the sign) was significant during the day but not at night. During the day, participants were less likely to miss an object when the beacons were above the sign.

Link between pavement marking retroreflectivity and night crashes on Michigan two-lane highways

The retroreflectivity of longitudinal pavement markings is expected to improve safety on rural highways. However, the few available research reports focused on the relationship between retroreflectivity and safety have found mixed results. New insights into such a relationship by using generalized linear mixed-effects models are provided. With this tool, the research team developed and analyzed a database of rural two-lane roads in Michigan, including night crashes, roadway characteristics, and retroreflectivity of pavement markings. The analysis used crash data from 2003 through 2008 for select types of nighttime crashes. The analysis found a statistical association between pavement marking retroreflectivity and nighttime safety. A significant statistical interaction between white edgeline and yellow centerline retroreflectivity indicated that these variables performed interdependently. In general, sites with higher retroreflectivity were found to be associated with fewer crashes than sites with lower retroreflectivity for both types of markings. This research also found that sites with low centerline retroreflectivity (compared with edgeline retroreflectivity of the same road) were associated with more crashes.

Comparison of Above-Sign and Below-Sign Placement of Rectangular Rapid-Flashing Beacons

Several methods have been used to emphasize the presence of a pedestrian crossing, including supplementing signing with beacons. A device that has received national attention is the rectangular rapid-flashing beacon (RRFB). A question being asked is whether the position of the beacons above or below the pedestrian crossing sign influences the effectiveness of the treatment. A closed-course study found that at night RRFBs located above the crossing sign offered advantages compared with LEDs located within or below the sign. To determine if the position of the beacons affected driver yielding, RRFBs were installed above and below the pedestrian crossing sign at 13 sites in four locales. A staged pedestrian protocol was used to collect driver yielding to ensure a consistent presentation of approaching pedestrians. Preliminary findings showed only minor, if any, differences between the above and below positions (average daytime yielding for staged pedestrians was 64% for above and 61% for below), and the statistical test showed no significant difference. The open-road study found that the position of the RRFB did not affect a driver’s decision to yield. With apparent benefits identified from the closed-course study—i.e., lower discomfort and improved ability to detect the pedestrian as measured by identifying the direction a cutout photo of a pedestrian is traveling—and the lack of difference in driver yielding as a result of position, locating the beacons above the warning sign could improve the overall effectiveness of this treatment. As a result of these findings, FHWA plans to issue an official interpretation permitting placement of the beacons above the crossing warning sign.

Supervised association rules mining on pedestrian crashes in urban areas: identifying patterns for appropriate countermeasures

ABSTRACT In 2011, 4,432 pedestrians were killed (14% of total traffic crash fatalities), and 69,000 pedestrians were injured in vehicle-pedestrian crashes in the United States. Particularly in Louisiana, vehicle-pedestrian crashes have become a key concern because of the high percentage of fatalities in recent years. In 2012, pedestrians were accounted for 17% of all fatalities due to traffic crashes in Louisiana. Alcohol was involved in nearly 44% of these fatalities. This research utilized ‘a priori’ algorithm of supervised association mining technique to discover patterns from the vehicle-pedestrian crash database. By using association rules mining, this study aims to discover vehicle-pedestrian crash patterns using eight years of Louisiana crash data (2004–2011). The results indicated that roadway lighting at night helped in alleviating pedestrian crash severity. In addition, a few groups of interest were identified from this study: male pedestrians’ greater propensity towards severe and fatal crashes, younger female drivers (15–24) being more crash-prone than other age groups, vulnerable impaired pedestrians even on roadways with lighting at night, middle-aged male pedestrians (35–54) being inclined towards crash occurrence, and dominance of single vehicle crashes. Based on the recognized patterns, this study recommends several countermeasures to alleviate the safety concerns. The findings of this study will help traffic safety professionals in understanding significant patterns and relevant countermeasures to raise awareness and improvements for the potential decrease of pedestrian crashes.

Operating Speed on a Buffer-Separated Managed Lane

Managed lanes typically are on or adjacent to freeways and are actively operated and managed to preserve operational performance—such as more optimal travel speeds—over comparable general-purpose traffic lanes. A study was conducted to evaluate speeds on existing buffer-separated managed lanes to identify variables that influence operating speed. Speed data from more than 130 unique sites in Los Angeles, California; Orange County, California; and Dallas, Texas, were used. All analyses showed that the managed lane volume and the speed in the general-purpose lanes were related to the speed in the managed lane (statistically significant). The Dallas analysis, which used speeds averaged by 1-min increments, showed that the factor with the most influence on uncongested managed lane speed was the managed lane’s geometry. The relationship between uncongested managed lane speed and the managed lane envelope (sum of left shoulder width, managed lane width, and buffer width) was found to be statistically significant. For each additional foot over a 16-ft envelope width, managed lane speed increased by approximately 3.2 mph. In contrast, the California analysis, which used speeds averaged by 1-h increments, showed that the variable having the most influence was the volume in the managed lane. The researchers theorized that the lack of a relationship between managed lane speed and geometry in California is related to those speeds being an average 1-h speed rather than the 1-min speeds available in Texas.

Validation Technique Applied to Oregon Safety Performance Function Arterial Segment Models

The Oregon Department of Transportation developed segment arterial safety performance functions (SPFs) to help quantify the safety performance of driveways located on state urban and rural arterial highways. The research team determined that the crash reporting indicating that a driveway may have been involved in the crash was not a dependable variable, so the team developed SPFs for all non-intersection-related arterial crashes (many were likely the result of vehicle interactions at driveway locations). The information included in this paper reviews the subsequent validation effort and highlights innovative techniques used for the analysis. A common validation approach is assessing model performance for spatial transferability. For this effort, however, the authors evaluated spatial transferability, spatial–temporal transferability, and individual coefficient stability and significance. These procedures were highlighted and applied to an example urban model. The model performed well with the spatial transferability resulting in statistically equivalent values. The spatial–temporal transferability provided similar values but was not statistically equivalent at the 95% level, and all but one of the model variables were determined to be statistically significant.

Identifying low-volume road segments with high frequencies of severe crashes

Low-volume two-lane highways can be characterized by a wide range of physical features. Often the available crash data for these facilities are limited to fatal and injury crash information. It can be a challenge, therefore, to determine whether the select number of severe crashes observed along a corridor merits detailed safety evaluations and the associated investment of limited funds. The technique identified in this paper uses predictive method concepts developed with procedures consistent with those included in the AASHTO Highway Safety Manual but targeted only to low-volume roads and the number of observed fatal and injury crashes. For the purposes of this analysis, safety models are based on detailed crash and site data for low-volume highways in the state of Washington. A simplified procedure is then demonstrated to determine whether the number of severe crashes (fatal and injury) is significant enough to justify a detailed safety assessment and potential special safety enhancements on roadway construction projects or stand-alone safety enhancement projects for low-volume (≤1,000 vehicles per day) rural two-lane highways.