Changeable Message Sign Research Articles

Task-Relevant Smartphone Messages Within Work Zones: A Driving Simulation Study.

This study explored the impact of in-vehicle messages relative to roadside messages to alert drivers to events within a simulated work zone, in order to determine if these messages can improve driving performance within the work zone. Safety risks in work zones are usually mitigated by design standards and clear signage to communicate work zone information to drivers. Due to distraction and other driving task demands, these signs are not always noticed by motorists, nor are they always followed when they are noticed. The driving simulation tested drivers in two different types of work zones, shoulder work, and lane closure. Participants drove through these work zones three times, each with different messaging interfaces to communicate hazardous events to the driver. The interfaces included a roadside, portable changeable message sign, a smartphone presenting only auditory messages, and a smartphone presenting audio-visual messages. There was significantly better driving performance on key metrics including lane deviation for the in-vehicle message conditions relative to the roadside signs. Furthermore, drivers directed visual attention toward the roadway for the in-vehicle message conditions relative to the roadside sign condition. The results indicate that in-vehicle messaging could provide benefits to primary task performance in driving if the message content is appropriately designed. The findings provide support for a design framework to support in-vehicle communication to drivers approaching work zones and other environments to safely alert them to hazards.

Implementation of two robotic flagmen controlled by CAN messages to increase the safety of human workers in road maintenance

Commonly, the improper signaling in road construction zones is the cause of different accidents to drivers, pedestrians, and road construction workers. The signaling used when a vehicle is approaching a repairing section could be classified into two classes: stationary or active. Nevertheless, active warning systems have demonstrated to reduce accidents in road work zones. Within the active signaling class we have: portable changeable message sign, flashing arrow signs, flagman, to mention some. This paper describes the implementation of two robotic flagmen controlled by the Controller Area Network (CAN) protocol. Each robotic flagman can perform four different actions: speed reduction (right and left) and lane change (right and left). The electronic circuitry and mechanical motors of the two robotic flagmen have the option to be powered by a solar charging system considering working zones where there is no access to the electric grid. The solar charging system guarantees a sufficient electrical power supply for night conditions operations. Also, the CAN protocol can be used to monitor the correct operability of the robotic flagmen thus eliminating the need to incorporate more expensive electronic devices such as cameras. The hardware combination in the control, monitoring, and solar charging system allow us to propose a low-cost practical implementation. The results of our implementation show that the longest response time of the robot is less than 850 ms once that the CAN message has been sent to the network. This demonstrates that our proposal can meet real-time implementation requirements.

Determining the effective location of a portable changeable message sign on reducing the risk of truck-related crashes in work zones

Truck-related crashes contribute to a significant percentage of vehicle crashes in the United States, which often result in injuries and fatalities. The amount of truck miles traveled has increased dramatically with the growing rate of freight movement. Regarding truck crashes in the highway work zones, many studies indicated that there was a significant increase in crash severity when a truck crash occurred in work zones. To mitigate the risk of truck crashes in work zones, a portable changeable message sign (PCMS) was frequently utilized in addition to standard temporary traffic control signs and devices required by the Manual on Uniform Traffic Control Devices. To justify the use of a PCMS in work zones, there is a need to study the effective location of a PCMS deployed in a work zone by measuring the changes of truck and passenger car speed profiles. The difference of speed changes between trucks and passenger cars was considered as one of the major reasons which caused truck-related crashes in work zones. Therefore, reducing the difference of speed changes between trucks and passenger cars could potentially improve safety in work zones. The outcomes of this study will provide required knowledge for traffic engineers to effectively utilize the PCMS in work zones with the purpose of reducing truck-related crashes. In addition, the success of this study will provide a roadmap to investigate the effective deployment of other temporary traffic control devices on mitigating the risk of truck-related crashes in work zones.

Placement Design of Changeable Message Signs on Curved Roadways

ABSTRACT This paper presented a fundamental framework for Changeable Message Sign (CMS) placement design along roadways with horizontal curves. This analytical framework determines the available distance for motorists to read and react to CMS messages based on CMS character height, driver's cone of vision, CMS pixel's cone of legibility, roadway horizontal curve radius, and CMS lateral and vertical placement. Sample design charts were developed to illustrate how the analytical framework may facilitate CMS placement design.

Test a Queue Detection System for Special Events in Nevada

Queue detection systems have been used in traffic management in work zones and have also been recommended for traffic control for special events like sports and conventions. However, they have not been tested in the field. This paper presents the results of tests for a queue detection system at two special events in Las Vegas, Nevada. The system consisted of two vision detectors, radio frequency communications and one changeable message sign. Two aspects of the system were evaluated: the effectiveness of the system in reducing speeds and the cost and effectiveness of its deployment. In the tests, traffic data such as queue length and vehicle operating speeds were collected and analyzed to see whether motorists respond congestion related message on the changeable message sign when they did not perceive the congestion. By this approach, the motorists’ true responses to the system were identified. The results indicated that motorists did make positive responses to the messages provided by the system. However, it was found that the system may not be cost-effective because significant costs would be incurred in purchasing, installation and maintenance of the system. Recommendations were provided to utilize existing message signs and detectors to provide the same information to motorists as a queue detection system does.

Driver Feedback on Monetary Penalty and Its Impact on Work Zone Speed

Across the nation, one work zone fatality occurs every 10 h (about 2.3 per day) and one injury, every 13 min (110 per day). Speed limit compliance in and around work zones concerns transportation agency officials because excessive speeds have proved to be primary causes of crashes in work zones. As much as 25% of fatal crashes in work zones may have involved high speeds. Research was conducted with the use of a changeable message sign with radar (CMSR) at one work zone location on a four-lane, divided highway in Arizona. The CMSR, which was triggered by radar-detected speed, provided feedback to drivers about the amount of their potential traffic fine. A review of the literature indicated that this type of feedback has received only limited study. The CMSR alternated one speed feedback message, “Your Speed XX mph,” with another, “Possible Fine $XXX.” The dollar amount varied according to the speed of the vehicle. The coupling of speeding-fine feedback with alternating feedback on vehicle speed led to an observed reduction of speeds in the tested work zone. Reductions in mean speeds were modest, at approximately 4 mph. However, the impact on excessive speeders was significant. The number of speeders that traveled 5 and 10 mph, or more, above the speed limit decreased by one-fourth. At the extreme speeds of 15, 20, and 25 mph over the speed limit, the number of speeding vehicles was reduced in each case by half.

Intelligent Vehicular Warning System for VANET

The vehicular ad hoc network (VANET) has made significant progress in recent years, attracting a lot of interest from academia and the industry. VANET involves vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications based on a wireless network. V2I refers to the communication between vehicles and infrastructure of roadside unit (RSU), e.g., a base station and access point (AP) connected to the Internet. V2V refers to the direct or multi-hop communications among vehicles in VANET. V2V is efficient and cost effective owing to its short range bandwidth advantage and its ad hoc nature. V2V communications are enabling technologies that enhance the driver’s awareness of nearby vehicular traffic, leading to improved traffic safety and efficiency. The V2V mode provides a communications platform between road vehicles (cars, bikes, scooters, motorcycles, trucks, etc.) without requiring a central control unit. Safety-related V2V applications are enabled via an integrated early warning mechanism. To facilitate safe driving, we propose an Intelligent Vehicular Warning System (IVWS) that sends an immediate warning message in the event of an accident. According to V2V communications, the other cars or vehicles could have enough time to avoid the accident and make an appropriate decision such as slow down, stop, and detour after receiving the urgent warning messages. Furthermore, the local CMS (Changeable Message Sign) can show the accident information for neighbor vehicles when receiving the warning message. To achieve experimental architecture with our proposed IVWS, the robot vehicles have been designed to simulate vehicles on the road. Besides, vehicles also apply ZigBee wireless interface to communicate with each other. The experiment has shown that our proposed intelligent system can initially provide message display and safety driving for vehicles when traffic accident occurred.

Synthesis of Unconventional Dynamic Merge Metering Traffic Control for Work Zones

This paper presents an unconventional approach for work-zone bottleneck traffic control through integrating the dynamic late merge with a merge metering via wireless communication at the downstream taper area of a work zone, termed as Dynamic Merge Metering Traffic Control System (DMM-Tracs). The architecture and communication system for the DMM-Tracs, including system components, communication technologies and operation mechanism, are introduced. With this system, the merge metering control will be activated depending on the volume detected at an upstream location of the work-zone bottleneck. If the thresholds of control parameters are met, a merge metering signal installed at the taper area will be activated and approaching vehicles will be informed of the metering situation through flashing signage or changeable message sign installed in the advance areas of the work zone. To reduce enforced merges and potentials of merge conflicts, the control scheme will be adjusted on the real-time basis depending on the detected traffic conditions. This potentially increases the efficiency with which the traffic is discharged into the open lane inside the work zone. A portable controller is the “brain” of the DMM-Tracs to receive data from detectors, process the data, and control the merge metering signal via wireless communications. The efficacy of the DMM-Tracs is evaluated via a microsimulation test bed with the state-of-the-art microscopic simulation software VISSIM. Meanwhile, the volume threshold values are also determined via the simulation. The simulation results indicate that higher lane-closure percentage of the bottleneck, more applicable the DMM-Tracs.

Analyzing motorists’ responses to temporary signage in highway work zones

For decades, the importance of highway work zone safety has increased considerably with the continual increase in the number of highway work zones present on highways for repairs and expansion. Rural work zones on two-lane highways are particularly hazardous and cause a significant safety concern due to the disruption of regular traffic flow. In this study, researchers determined motorists’ responses to warning signs in rural, two-lane highway work zones. The researchers divided vehicles into three classes (passenger car, truck, and semitrailer) and compared the mean change in speed of these classes based on three different sign setups: portable changeable message sign (PCMS) OFF, PCMS ON with the message of Slow Down, Drive Safely, and a temporary traffic sign (W20-1, “Road Work Ahead”). Field experiments were conducted on two two-lane work zones with flagger control. Statistical analyses were performed to determine whether there was a significant interaction between motorists’ responses and the sign setups. Data analysis results show that a visible PCMS, either turned on or off, was most effective in reducing truck speeds in rural, two-lane work zones. The temporary traffic sign (W20-1) was more effective in reducing the vehicle speeds of passenger car and semitrailer. Results of this research project will help traffic engineers to better design the two-lane work zone setup and take necessary safety countermeasures to prevent vehicle crashes.

Evaluation of Messages on Changeable Message Signs as a Speed Control Measure in Highway Work Zones

The objective of this study is to measure the effectiveness of three commonly used changeable message sign (CMS) messages in reducing vehicular speeds and variances in highway work zones. This paper presents the results of a field study conducted on Interstate-90 in western New York State to evaluate the use of three different types of messages displayed on a CMS, as a speed control measure. The study included speed measurements of nearly 180,000 vehicles. The three types of CMS messages tested were: (1) RIGHT∣LANE∣CLOSED∼KEEP∣LEFT; (2) WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP; and (3) LEFT∣LANE∣CLOSED∼KEEP∣RIGHT. Of the three CMS messages tested, the CMS message stating “WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP” proved the most effective, significantly reducing vehicle speeds by 3.3–6.7mi∕h(5.3–10.8km∕h). The other two CMS messages were not as effective. The standard deviation of speed for the CMS message: WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP increased by 1.1–1.7mi∕h(1.8–2.7km∕h) in the driving lane and 0.2–2.0mi∕h(0.3–3.2km∕h) in the passing lane. The speed variances for the other two CMS messages ranged from −2.00to1.13mi∕h (from −3.23km∕hto1.83km∕h).

Impacts on Traffic Diversion Rates of Changed Message on Changeable Message Sign

The Ontario Ministry of Transportation has installed 27 changeable message signs (CMSs) strategically upstream of express–collector transfer locations on Highway 401 in Toronto, Ontario, Canada. Motorists are informed by the CMSs of traffic conditions downstream of the transfer location to help them decide whether to take the next transfer. Loop detectors are installed at the transfer locations to measure traffic flow. The dynamic impacts of CMS messages on traffic diversion are evaluated by using 3 years of loop detector data, from 2003 to 2005. Time-series plots of aggregated diversion rates show that the initial transient response to the message change is significant and that, in addition to the messages themselves, the occurrence of a message change plays a vital role in influencing downstream diversion. Aggregate diversion rate plots also reveal that the logic underlying the Highway 401 CMSs may be causing the signs to react to diversion rate changes on many occasions, thereby closing a feedback control loop that effectively regulates the downstream diversion rates.

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 (America's 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.

Highway Traffic Response to Dynamic Fog Warning and Speed Advisory Messages

The response of traffic to messages displayed on a changeable message sign (CMS) warning of fog ahead and advising specific speeds at increasingly lower visibility levels is examined. Over a 2-year period, the speed, length, and time of detection were individually recorded for all vehicles at four sites: two before and two after a CMS. Mean speed, speed variance, and potential collision speed (PCS), a new metric, were calculated with a 45-s moving window and averaged over each constant message state. PCS is a predictor of impact speed in a potential chain collision that considers visibility as well as speed and separation between individual vehicles. When the CMS was activated, mean traffic speed decreased 1.1 mph on average over all fog events in comparison to mean speed in the absence of a message. However, average PCS increased differentially by 8 mph because of platoon compression and the sensitivity of this metric to increasingly worse visibility after the CMS during most activations. Speed standard ...

Highway Traffic Response to Dynamic Fog Warning and Speed Advisory Messages

The response of traffic to messages displayed on a changeable message sign (CMS) warning of fog ahead and advising specific speeds at increasingly lower visibility levels is examined. Over a 2-year period, the speed, length, and time of detection were individually recorded for all vehicles at four sites: two before and two after a CMS. Mean speed, speed variance, and potential collision speed (PCS), a new metric, were calculated with a 45-s moving window and averaged over each constant message state. PCS is a predictor of impact speed in a potential chain collision that considers visibility as well as speed and separation between individual vehicles. When the CMS was activated, mean traffic speed decreased 1.1 mph on average over all fog events in comparison to mean speed in the absence of a message. However, average PCS increased differentially by 8 mph because of platoon compression and the sensitivity of this metric to increasingly worse visibility after the CMS during most activations. Speed standard deviation among proximate vehicles did not appear to be significantly affected—within 5 to 7 mph across all lanes in most cases. The warning messages evoked a measurable effect on driver behavior but well below design expectations. Drivers appeared to respond predominantly to their own perceptions and reduced speeds in fog, but not nearly enough to compensate for the reduced visibility. When the advised speed was 30 mph in dense fog, mean speeds averaged 61 mph.

Improving Compliance with Work Zone Speed Limits

Thousands of crashes occurring in work zones each year lead to numerous fatalities and injuries. The sizeable portion of these crashes attributed to excessive speed emphasizes the need to motivate drivers to comply with speed limits in work zones. A recent research project was conducted to determine effective measures to motivate and encourage drivers to observe posted speed limits in work zones. Three devices were tested in that project: a speed display trailer, changeable message sign with radar, and orange-border speed limit sign. Results from field testing indicate that devices with the ability to display drivers’ speeds have considerable potential for reducing speeds and improving compliance. Orange borders greatly improve the visibility and conspicuity of speed limit signs, but they do not have a consistent measurable effect on compliance. In the absence of active enforcement, data from this project indicate that drivers are likely to drive as fast as they feel comfortable, regardless of the posted speed limit.

Improving Compliance with Work Zone Speed Limits Effectiveness of Selected Devices

Thousands of crashes occurring in work zones each year lead to numerous fatalities and injuries. The sizeable portion of these crashes attributed to excessive speed emphasizes the need to motivate drivers to comply with speed limits in work zones. A recent research project was conducted to determine effective measures to motivate and encourage drivers to observe posted speed limits in work zones. Three devices were tested in that project: a speed display trailer, changeable message sign with radar, and orange-border speed limit sign. Results from field testing indicate that devices with the ability to display drivers' speeds have considerable potential for reducing speeds and improving compliance. Orange borders greatly improve the visibility and conspicuity of speed limit signs, but they do not have a consistent measurable effect on compliance. In the absence of active enforcement, data from this project indicate that drivers are likely to drive as fast as they feel comfortable, regardless of the posted ...

Evaluating Speed-Reduction Strategies for Highway Work Zones

Research was conducted to identify the potential of fluorescent orange sheeting, innovative message signs, and changeable message signs with radar for reducing speeds in highway work zones. The study investigated the effect of each strategy immediately after implementation (immediate effect) as well as several weeks after implementation (novelty effect). In addition to the overall effect of each strategy on all vehicles, the study included the effect on specific vehicle types during various lighting conditions. The researchers collected traffic data before, immediately after, and 2 or 3 weeks after implementation of each strategy (3 consecutive weeks for the changeable message sign). They collected data upstream of the temporary traffic-control zone, in the advancewarning area, and adjacent to the active work area. The researchers used various statistical tests to evaluate the significance of speed changes from phase to phase and adjusted vehicle speeds with the upstream speed changes over time. The study indicated that fluorescent orange sheeting and innovative message signs help reduce speeds at highway work zones (with diminished influence over time). Moreover, both strategies influence vehicle speeds more during the day than at night. Drivers of passenger vehicles tended to decrease their speeds more than did truck drivers. Changeable message signs with radar significantly reduced the vehicle speeds in the immediate vicinity of the sign and did not demonstrate a novelty effect.

Fatigue-Life Evaluation of Steel Post Structures. I: Background and Analysis

Changeable message sign (CMS) structures are cantilever, interverted L-shaped structural com- ponents that are used to transmit information on road conditions to the driving public. The high-cycle fatigue failure of one CMS structure in southern California led to a detailed analytical and experimental study of CMS structures. In this paper key data from field studies are presented together with results of finite-element studies of CMS structural components. A companion paper documents the results of the experimental program and presents recommendations for future CMS construction. Analysis of field data shows mechanical damping in CMS structures to be approximately 0.5% of critical in the first two modes and that galloping instability was probably the cause of failure of the CMS structure. Finite-element models were developed for one as-built post, one gusset-retrofitted post, and different conduit hole geometries. The finite-element analysis showed that there were high stress concentrations around the conduit holes in all cases, that conduit hole geometry appears to play only a small role in the value of maximum stress, and that the gussets served to reduce the longitudinal and von Mises stresses at the post-baseplate weldment but not around the conduit hole where the gussets created stress risers at the gusset tip.

Changeable Message Sign Messages for Work Zones: Time of Day, Days of Week, and Month Dates

The New Jersey Department of Transportation initiated a research study designed in part to further the state of knowledge of changeable message sign message design with specific application to the needs in New Jersey. Laboratory studies of human factors are described here; the studies were conducted in New Jersey to evaluate shorter alternative messages than those currently used to display time of day, days of week, and calendar dates. These types of messages are often displayed on portable changeable message signs used in highway work zones. Among the findings were that a dash can be used instead of the term Thru to indicate roadwork for a range of successive days; the term Weekend is not a good descriptor for work that begins on Friday evening and ends on Monday morning; the term Days did not connote specific daytime, off-peak times for roadwork, but it may be satisfactory for certain time periods; likewise, the term Nights did not connote specific nighttime, off-peak times for roadwork, but it may be satisfactory for certain time periods; Nite is an acceptable substitute for Night; and calendar dates were not easily translated by drivers to specific days of the week.

San Diego Field Operational Test of Smart Call Boxes: Technical Aspects

Smart call boxes are devices similar to those used as emergency call boxes in California. The basic call box consists of a microprocessor, a cellular transceiver, and a solar power source. The smart call box system also includes data-collection devices, call-box maintenance computers, and data recording systems at a central location. The goal of the smart call box field operational test (FOT) was to demonstrate that smart call boxes are feasible and cost-effective means of processing and transmitting data for tasks such as traffic census, incident detection, hazardous weather reporting, changeable message sign control, and video surveillance. The objective of the FOT evaluation was to determine the cost-effectiveness of smart call boxes, but because of schedule slippage the evaluation focused on only functional adequacy and capital costs. The concept for the smart call box system was found to be feasible but not necessarily optimal for the tasks involved. System integration was a major problem. Also, the number of external devices that can be attached to a single call box while maintaining the economic advantages of the system is restricted by wiring costs and limitations of the solar power supply. Test system performance was mixed. One subtest was canceled before the installation of equipment, functional systems were produced for only three of the four remaining subtests, and reliable operation was observed in only one case. In most cases, system costs will be dominated by the expense of installing wiring. Consequently, smart call boxes will be cost-effective compared with hardwire systems at many sites but may not be cost-effective compared with alternative wireless systems.