Steven D Schrock

Feasibility of real-time remote speed enforcement for work zones

Studies have shown that a large percentage of vehicles involved in work zone crashes are traveling at excessive speeds. Although traditional speed enforcement has been shown to reduce speeds through the work area, enforcement under these conditions can be dangerous to both the motoring public and enforcement officers. The work zone layout often limits the locations at which an officer can set up to enforce the speed limit and the locations at which violators can be stopped. Automated speed enforcement technology could help eliminate the need to stop violators in a work zone, but it is not currently a popular concept in the United States because of concerns about motorist privacy. Researchers hypothesized that this technology could be useful for work zone enforcement if adapted to a more real-time operation. The initial testing of the concept of remote speed enforcement is summarized. An automated speed enforcement system (consisting of digital video and lidar technology) was meshed with a wireless communications system. The unit determined when vehicles exceeded a certain speed threshold. If a vehicle was detected as exceeding the threshold, a digital photograph was taken of the violator. This photograph was then transmitted to an observer stationed downstream of the site. The technical feasibility of the system was assessed through field tests. Focus groups of law enforcement personnel were used to determine potential acceptance of the system in the law enforcement community. Recommendations for future improvements and possible applications of the system are made.

Flashing Message Features on Changeable Message Signs

Studies were conducted with a driving simulator to determine the effects of displaying changeable-message-sign messages with dynamic features consisting of (a) flashing all lines simultaneously in a one-phase, three-line message and (b) flashing one line (top line) of a one-phase, three-line message. In the first dynamic feature, all three lines were flashed. Only the top line was flashed for the second dynamic feature. Messages with these two dynamic features were compared with comparable static messages. No differences in average reading time were found between the messages in which all three lines flashed and static messages. However, the results suggest that flashing an entire one-phase message may have adverse effects on message understanding for drivers who are unfamiliar with this dynamic mode of display. A significant percentage of the subjects preferred the static display. The average reading time for the flashing line (top line) messages was significantly longer than for the static messages. The results also suggest that unfamiliar drivers will be adversely affected by this particular display feature, relative to comprehension of the entire message. The subjects liked the flashing line and static messages equally well. No differences were found by age, education, and gender among the three dynamic message modes and their alternatives. In addition, no differences were noticed in driving performance.

Survey of State Law Enforcement Personnel on Work Zone Enforcement Practices

An important first step in maximizing the effectiveness of work zone law enforcement is to determine how officers operate. Although transportation professionals may understand the benefits of different enforcement strategies, does this translate to improved enforcement methods in the field? A survey was developed and administered to determine the problems encountered by various state law enforcement agencies when enforcing work zones. The survey was also an attempt to identify areas of improvement and innovative practices worthy of further development. State law enforcement agencies from 20 states were contacted by telephone to determine how work zones were enforced in their respective states. Officers were asked questions regarding funding for work zone enforcement; techniques used by law enforcement at work zones; locations in or near work zones where officers are typically stationed; the level of coordination between law enforcement, the state highway authority, and the construction contractor; and initiatives that helped maximize the effectiveness of law enforcement in work zones. A strategy identified in this research was the formation of specialized units to patrol work zones and to train other officers to effectively patrol work zones. A second strategy allows local law enforcement officers and retired officers the opportunity to enforce work zone practices on state roadways to overcome a chronic shortage of available officers.

Effectiveness of Lane Direction Arrows as Pavement Markings in Reducing Wrong-Way Movements on Two-Way Frontage Roads

The principal objective of this research was to conduct a before-and-after study of the impacts of using lane direction arrows on a two-way frontage road to determine if the arrows could reduce wrong-way movements for vehicles exiting the freeway. A recent national survey related to all-white pavement markings indicated that 94% of the 851 drivers surveyed correctly interpreted the intended meaning of the arrows to indicate the proper lanes for travel. The authors believed that this high comprehension rate could be useful in helping drivers at locations where a potential for driving in the wrong direction exists. Video surveillance of a two-way frontage road before and after installation of lane direction pavement marking arrows was conducted. It was observed that at the selected location, approximately one of every 13 drivers exiting the freeway to the frontage road acted as though the frontage road were a one-way section and incorrectly chose the left lane for travel. Significant reductions were observed in wrong-way driving after the installation of two lane direction pavement marking arrows downstream from the exit ramp. After the installation, only one of 150 vehicles selected the incorrect lane. Researchers concluded that lane direction pavement marking arrows had a beneficial effect on safety at the study location and recommended expanded efforts to determine other locations that could benefit from this treatment. Although the evaluation was limited to one study site, the strength of the results suggests that the treatment would be beneficial at other similar locations.

Closed-Course Test and Analysis of Vibration and Sound Generated by Temporary Rumble Strips for Short-Term Work Zones

Driver distraction and speeding are two contributors to crashes in construction and maintenance work zones. Rumble strips can be effective and have been used in some states to alert drivers to reduce speed in advance of some change in the driving situation, such as at intersections. Previous research has examined the potential of using temporary rumble strips in advance of work zones. The purpose of this research was to compare the attention-getting characteristics of several temporary rumble strips with permanent rumble strips. Two types of devices were tested and compared with permanent rumble strips: portable plastic rumble strips and adhesive rubberized polymer rumble strips. These devices were tested for their ability to generate steering wheel vibrations and in-vehicle and roadside sound. Analysis revealed that the portable plastic rumble strips were more effective on cars than on trucks for generating in-vehicle vibration and increasing the in-vehicle sound level. Further, they were generally better than the adhesive rumble strips in matching the characteristics of the tested permanent rumble strip. This was also true for the configurations that contained fewer than six portable plastic rumble strips. If the vibration and sound generated by the permanent rumble strips is considered the standard performance, various configurations of the portable plastic rumble strips can be implemented in short-term work zones and provide results similar to those of permanent rumble strips.

A Closed-Course Feasibility Analysis of Temporary Rumble Strips for Use in Short-Term Work Zones

This research was conducted to determine how best to incorporate portable rumble strips into traffic control plans for short-term work zones. One objective of the research was to provide guidance on how existing traffic control plans could be amended to include provisions for the evaluated devices. This research focused on rumble strips that were considered beneficial for any type of work zone where the duration is one day or less. The tests on the portable rumble strips were conducted on a closed roadway surrounding the Kansas Speedway in Kansas City, Kansas, and in a closed park-and-ride parking facility in Lawrence, Kansas. The rumble strips tested in this study were two different types of reusable temporary rumble strips made out of steel with a rubber bottom and four generations of plastic rumble strips. From this study the best solution for most short-term work zones would be the latest generation of plastic rumble strips tested. The earlier generations did not perform as well as the fourth generation especially at 60 mph (96.6 km/hr). The steel rumble strips also hold some promise; however, the structural integrity of the steel rumble strips is an issue that needs to be addressed.

Implications of Distracted Driving on Start-Up Lost Time for Dual Left-Turn Lanes

Previous research has found that distracted driving measurably increases driver response times to unanticipated roadway hazards. These instances are of particular consequence as they tend to be highly correlated with vehicle crashes resulting in property damage and/or injury. However, comparatively little attention has been allocated to quantifying the negative impacts of distracted driving on driver reaction to anticipated stimuli. This study empirically determined the impact of distracted driving on queue discharge rates at signalized intersections with protected left turn phases for dual left turn lanes. Observational studies were conducted at 11 intersection approaches at six signalized intersections in three states resulting in the observation of 844 distracted and 3,726 undistracted left turning drivers. A statistical model was developed for the startup lost time resulting from the average headways of the samples in each state. The difference in startup lost times between queues comprised entirely of distracted or undistracted drivers

Estimation of safety effectiveness of composite shoulders on rural two-lane highways

A paved shoulder is regarded as an effective safety improvement to reduce crashes. It is believed that there is a diminishing safety benefit for each additional increment of paved shoulder over a certain width. Thus, there might be greater systemwide safety benefits from paving longer roadway segments with a composite shoulder than from paving shorter roadway segments with a full-width paved shoulder. The objective of this study was to determine the safety benefits of composite shoulders, such as a small paved shoulder combined with turf on the outside. This approach was part of the Kansas Department of Transportations effort to find practical improvements to maximize the benefits of shoulders relative to the input costs. Of the 8,300 mi (13,358 km) of rural two-lane highways in Kansas, approximately 25% are equipped with composite shoulders consisting of 3 ft (0.9 m) of pavement, with the remainder being turf. The safety effectiveness of these shoulders was studied with a combined empirical Bayes method. Three safety performance functions were used to create Kansas-specific crash modification factors for composite shoulders compared with segments with no or unpaved shoulders. It was found that upgrading narrow unpaved shoulders to composite shoulders could reduce shoulder-related crashes by up to 61% and fatal and injury crashes by 31%. On the basis of these results, 20-year projections were developed that estimated the safety effectiveness that could be achieved through the implementation of these safety improvements.

Estimation of Safety Effectiveness of Widening Shoulders and Adding Passing Lanes on Rural Two-Lane Roads

There is a need to evaluate the costs and benefits of potential safety improvements so that limited budgets for low-volume roads may be used most effectively. Increasing the width of shoulders and adding passing lanes have been regarded as economical and effective safety improvements. The state of Kansas has more than 2,000 mi (3,219 km) of highway that may need these improvements, most of which are rural two-lane roads. This study considered how historical data and crash modification factors (CMFs) were combined to estimate the safety benefits of widening shoulders and adding passing lanes on rural two-lane roads. The objective was to determine specific CMFs for the state of Kansas and states with similar rural environments as well as to estimate the number of crashes avoided. Safety and traffic volume data for rural two-lane roads from 2000 to 2008 were obtained from the State of Kansas and combined with existing models from earlier studies to create state-specific CMFs to more accurately estimate safety benefits. It was determined in this study that CMFs for shoulder widening and the addition of passing lanes for low-volume roads are 0.95 and 0.65, respectively. These CMFs are based on shoulder widening from 2 ft (0.61 m) to 8 ft (2.44 m) or construction of a short four-lane passing section. From these results, 20-year projections were developed for the benefits in crash reductions that could be achieved through implementing these safety improvements.

License Plate and Telephone Numbers in Changeable Message Sign Amber Alert Messages

Studies were conducted with a driving simulator and laptop computers to determine the effects of displaying license plate and 10-digit telephone numbers in Amber (Americas Missing: Broadcast Emergency Response) alert changeable message sign messages. The first study was conducted using the Texas Transportation Institute driving environment simulator in College Station, Texas. A laboratory study was also conducted in six cities in Texas. It was found that the average reading time for Amber alert messages with a license plate number was significantly longer than for messages without a license plate number. In addition, the majority of subjects were not able to recall the entire number. A license plate number was found to be equivalent to more than three units of information. Thus a message with a license plate number exceeds current effective message design guidelines that specify a maximum of four units of information in a message and a maximum of three units of information in a message phase. Similarly, the average reading time for messages with a 10-digit telephone number is significantly longer than for messages without a telephone number. The majority of subjects were not able to recall the entire number. A telephone number was found to be equivalent to more than three units of information. A message with a 10-digit telephone number exceeds current effective message design guidelines.