Changeable Message Signs Research Articles

EVALUATION OF TWO METHODS OF PROMPTING DRIVERS TO USE SPECIFIC EXITS ON CONFLICTS BETWEEN VEHICLES AT THE CRITICAL EXIT

The Florida Department of Transportation used a series of changeable-message signs that functioned as freeway guide signs to divert traffic to Universal Theme Park via one of two eastbound exits based on traffic congestion at the first of the two exits. An examination of crashes along the entire route indicated a statistically significant increase in crashes at the first eastbound exit following the actuation of the system. Furthermore, all of the crashes occurred in close proximity to the exit gore (the crosshatched area at exits that drivers are not supposed to enter or traverse) at the first exit. In Experiment 1, behavioral data were collected using an alternating treatments design. These data revealed that reassigning the exit signs was effective in producing a change in the percentage of drivers using each of the two exits. These data also showed that the reassignment of the theme park exit was associated with an increase in the percentage of motor vehicle conflicts that consisted of vehicles cutting across the exit gore. An analysis revealed that the method used for switching the designated or active theme park exit on the series of changeable-message signs led to the presentation of conflicting messages to some motorists, thus resulting in erratic driving behavior (cutting across the exit gore). In Experiment 2, the treatment evaluated the use of a phased method of switching the designated theme park exit to eliminate the delivery of conflicting messages. The new method for switching the designated theme park exit was not associated with an increase in motorists cutting across the exit gore.

Legibility Distances of Smaller Letters in Changeable Message Signs with Light-Emitting Diodes

This paper presents the results of a legibility study of 9-in. and 10.6-in. letters on changeable message signs (CMSs) with light-emitting diodes. The study, conducted in Dallas, Texas, consisted of 60 subjects, demographically balanced with respect to age, gender, and education. The subjects drove a test vehicle as they approached CMSs with one of the above letter heights. Study administrators recorded the distance from the sign at which the participant could correctly read a three-letter word. Data were recorded for three trials on each of the letter heights for each participant. Data were collected during daylight (sun overhead) and nighttime conditions. The 85th percentile legibility distance for the 9-in. letter height was 228 ft for daytime conditions and 114 ft for nighttime conditions. For the 10.6-in. letter height, the 85th percentile legibility distances were 324 ft for daytime conditions and 203 ft for nighttime conditions, respectively. The 85th percentile legibility distances for each letter height were used to estimate available viewing times under various approach speeds. These available viewing times dictate the units of information that can be presented on a CMS of a particular letter size.

Legibility Distances of Smaller Letters in Changeable Message Signs with Light-Emitting Diodes

This paper presents the results of a legibility study of 9-in. and 10.6-in. letters on changeable message signs (CMSs) with light-emitting diodes. The study, conducted in Dallas, Texas, consisted of 60 subjects, demo-graphically balanced with respect to age, gender, and education. The subjects drove a test vehicle as they approached CMSs with one of the above letter heights. Study administrators recorded the distance from the sign at which the participant could correctly read a three-letter word. Data were recorded for three trials on each of the letter heights for each participant. Data were collected during daylight (sun overhead) and nighttime conditions. The 85th percentile legibility distance for the 9-in. letter height was 228 ft for daytime conditions and 114 ft for nighttime conditions. For the 10.6-in. letter height, the 85th percentile legibility distances were 324 ft for daytime conditions and 203 ft for nighttime conditions, respectively. The 85th percentile legibility distances for each letter height were used to estimate available viewing times under various approach speeds. These available viewing times dictate the units of information that can be presented on a CMS of a particular letter size.

Extending Older Drivers’ Access to Freeways with Intelligent Transportation System Technologies

The vanguard of the baby boom generation is approaching retirement age. They received their driver's licenses at the age of 16 at a time when freeways were reshaping urban land patterns. For those living in suburbs and the urban edge, freeway driving is a way of life. Nevertheless, as these drivers age, they too will experience changes in visual acuity and a reduction in their ability to respond quickly to changes in road conditions. Many studies document problems that older drivers face on city streets. The current study funded by the Arizona Department of Transportation and FHWA suggests that freeway driving might be less taxing for some. The study explores the possibility that intelligent transportation system (ITS) devices–-including variable message signs; portable, changeable message signs; and ramp meters–-may respond to older drivers’ challenges with freeway driving. Eleven focus groups held with diverse groups of freeway drivers from 65 to 80 years of age in 2003–2004 focused on these ITS devices and suggested minor changes in application that would enhance their value. Drivers said that fixed variable message signs with a positive contrast caught their attention and were easier to read than standard signs. They urged their use for short simple messages centered on the signs. Portable signs attracted attention, but they were subject to glare and were difficult to read at the roadside, particularly those with multiple phases. Ramp meters were enthusiastically endorsed especially when combined with acceleration lanes. A parallel study using Arizona accident data provided some statistical evidence to support positive views of ramp meters.

Extending Older Drivers' Access to Freeways with Intelligent Transportation System Technologies

The vanguard of the baby boom generation is approaching retirement age. They received their driver's licenses at the age of 16 at a time when freeways were reshaping urban land patterns. For those living in suburbs and the urban edge, freeway driving is a way of life. Nevertheless, as these drivers age, they too will experience changes in visual acuity and a reduction in their ability to respond quickly to changes in road conditions. Many studies document problems that older drivers face on city streets. The current study funded by the Arizona Department of Transportation and FHWA suggests that freeway driving might be less taxing for some. The study explores the possibility that intelligent transportation system (ITS) devices—including variable message signs; portable, changeable message signs; and ramp meters—may respond to older drivers' challenges with freeway driving. Eleven focus groups held with diverse groups of freeway drivers from 65 to 80 years of age in 2003-2004 focused on these ITS devices a...

Real time traffic information and its impacts on route switching behavior of expressway drivers

AbstractNon‐quantifiable factors (e.g. perceived, attitudinal and preferential factors) have not been investigated fully in past transportation studies, which has raised questions on the predictive capabilities of the models. In this study, Structure Integration Models, with one of their sub‐models, Measurement Equation, are combined with latent variables, which are integrated with another sub‐model, Structural Equation. The estimated latent variables are used as explanatory variables in decision models. As a result, the explanatory and predictive capabilities of the models are enhanced. The models can then be used to describe the various behaviors of travelers of different types of transportation systems in a more accurate way. In this study, the Structure Integration Model was applied to study the impacts of real‐time traffic information on the route‐switching behavior of road users on the Sun Yat‐Sen expressway, Taiwan. At present, the real‐time traffic information provided on this expressway includes radio traffic reports and changeable message signs. The results of this study can facilitate the provision of traffic information on highways.

A fuzzy queuing model for real‐time, adaptive prediction of incident delay for ATMS/ATIS

This paper presents a fuzzy queuing model that can be used to predict the possible delay that a vehicle will experience at an incident location based on real‐time information on current queuing conditions, traffic arrivals, lane closings. Compared to most existing methods, the proposed model is unique in three aspects. First, it explicitly accounts for uncertainties involved in all influencing factors and thus allows easy incorporation of imprecise and vague information typically available in this type of prediction environment. Second, the model is adaptive in the way that it allows continuous update of estimates as new information is made available. Third, delays obtained from the model are fuzzy numbers that can be conveniently mapped to linguistic terms for use in systems such as changeable message signs (CMS). A case study is presented to demonstrate the application of the proposed model in facilitating the composition of location‐dependent delay messages for CMS.

Application of Changeable Message Signs in Traffic

In the Republic of Croatia, changeable message signs are being introduced on high serviceable roads in order to improve the flow management in the network and increase the traffic safety level. The equipment installed in the past was not set according to the unique criteria, thus resulting in the installation of relatively incompatible equipment set in a disorganized manner. This work presents the basic guidelines in applying changeable message signs, primarily on the Croatian motorways. The types and levels of influence on the traffic are described, and the traffic and weather criteria for the application of changeable message signs are defined. The paper also analyzes the principles of installing the changeable message signs on roads and road facilities, recommending priorities in presenting the changeable signs.

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.

Deployment of Smart Work Zone Technology in Arkansas

The Arkansas State Highway and Transportation Department began an extensive pavement rehabilitation program in the spring of 2000 that ultimately will rebuild approximately 380 mi, or 60%, of Arkansas’ total Interstate miles. To improve safety and manage congestion in work zones, the department has deployed smart work zone technology systems on five projects. The main goal for this endeavor was to provide a queue-detection system that will prevent or reduce rear-end collisions and will also provide motorists with real-time information about potential backups caused by lane closures. After each system was installed, a general evaluation of the basic design was conducted. Knowledge gained was applied to each subsequent system, to improve the design and to provide increased effectiveness, reliability, and practicality. The design evolution of these systems is presented, the design development is discussed in detail, and the effectiveness of two of the automated work zone information systems installed on Interstate rehabilitation projects in Arkansas is evaluated. The systems used were ADAPTIR from Scientex Corporation and CHIPS from ASTI Transportation Systems. These systems included all hardware, software, and other equipment necessary for collecting, displaying, and processing traffic condition data. These data were used to provide motorists with real-time speed-control, delay, and diversion advisory messages via portable changeable message signs and a highway advisory radio system.

Guidelines for Application of Portable Work Zone Intelligent Transportation Systems

Work zone intelligent transportation systems (WZITSs) are promoted as a way to improve safety and reduce congestion at work zone locations where traditional traffic management centers do not exist. These systems usually integrate portable changeable message signs and speed sensors with a central control system that automatically determines appropriate messages that are based on current traffic conditions. Manufacturers of these systems claim that WZITSs can warn drivers of downstream congestion, alert drivers to slower speeds ahead, and suggest alternate routes on the basis of prevailing conditions. Transportation agencies are often asked to make decisions on the installation of a WZITS without the benefit of objective information on its expected performance. Relatively few operational tests of these systems have been performed, and the results are not always well documented or conclusive. Agencies need guidance to help them determine whether a WZITS system would improve safety and operations at a specific site. Applications of WZITSs are reviewed, and a series of guidelines for their deployment, based on lessons learned from past tests, is presented.

Determining Traffic Stream Impacts of Radar Detectors Using Microscopic Simulation

Police radar is known to have an effect on the speed of drivers. This effect derives from the presence of vehicles equipped with radar detectors in the traffic stream and the reactions that the drivers of these vehicles have to radar. The level of impact on a traffic stream exposed to radar transmissions is a function of the proportion of radar detector equipped vehicles in the traffic stream, i.e., the radar detector density. Microscopic simulation can be used to model this impact. A microscopic simulator extension is proposed that allows determinations of this type to be carried out by adding the capability to model driver response to radar transmissions. This approach can also be applied to the modeling of other driver warning technologies such as changeable message signs. A case study using the proposed methodology to analyze different congestion and radar detector density levels is presented and discussed. The case study shows that the efficacy of using radar as a speed reduction strategy is a function of congestion and radar detector density, with the strategy being most effective for volumes levels between 200 and 1,400 vehicles per hour per lane.

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.

Intertechnology Effects in Intelligent Transportation Systems

The expected benefits of varying combinations of intelligent transportation system applications, such as freeway service patrol, changeable message signs, and ramp metering, were examined. The research analyzed the simulated results of a stylized network in a microscopic traffic simulator. The traffic network included parallel roadways, ramp meters, and changeable message signs. These technologies were tested in various combinations. The effectivenesses were determined, and a measure of inter-technology economies was defined. In brief, additional technologies were found to be subadditive, and more benefits came from each technology in isolation than from the bundling of each with other technologies.

Flashing Messages, Flashing Lines, and Alternating One Line on Changeable Message Signs

Results of human factors laboratory studies conducted in Texas pertaining to the display of messages using the following dynamic characteristics of changeable message signs (CMSs) are presented: (a) the effect of flashing an entire one-frame message, (b) the effect of flashing one line of a one-frame message; and (c) the effect of alternating text on one line of a three-line CMS while keeping the other two lines of text the same. Two hundred sixty Texas drivers were recruited in Dallas, El Paso, Fort Worth, Houston, and San Antonio to participate in the laboratory studies designed to simulate these CMS characteristics on laptop computers. The drivers responded to questions designed to determine the level of recall and comprehension of the information contained in the message. Response times, message format, and sign operating preferences were also collected. The results showed that in the laboratory setting, flashing a one-frame message did not adversely affect driver recall or comprehension to a significant degree compared with when the message was not flashed. However, average reading times were significantly higher when the message was flashed. Flashing one line of a three-line message appeared to adversely affect recall of parts of the message. In addition, average reading times were significantly higher for the flashing line message. Alternating one line of text and keeping the other two lines constant did not adversely affect message recall. However, average reading times increased significantly.

Effectiveness of Condition-Responsive Advisory Speed Messages in Rural Freeway Work Zones

Condition-responsive advisory speed messages were evaluated as part of the Midwest States Smart Work Zone Deployment Initiative, a pooled-fund study sponsored by Iowa, Kansas, Missouri, Nebraska, and FHWA. The messages were displayed on three portable changeable message signs (PCMS) placed approximately 1.61 km (1 mi), 4.83 km (3 mi), and 12.87 km (8 mi) ahead of a work zone on a rural interstate highway in Nebraska. The messages were intended to advise drivers of the speed of slower traffic ahead and thereby encourage them to slow down. Speeds downstream of the PCMSs were measured and compared with the speeds displayed in the messages. The results of the analysis indicate that the messages were somewhat effective in reducing speeds. Their effectiveness could have been improved if the distances between the PCMSs had been shorter and thus the message locations would have been closer to the points with lower traffic speeds. Driver interviews revealed that the advisory speed messages were understood and thought to be useful by most drivers who had seen them. However, some drivers questioned their usefulness and doubted their reliability, because they had not seen any reason to slow down.

Development of a Test Protocol to Demonstrate the Effects of Secondary Tasks on Closed-Course Driving Performance

To assess the relative distraction potential associated with a variety of in-vehicle tasks, we developed a test protocol that provides an objective basis for demonstrating the tradeoffs between primary and secondary task performance in driving. The protocol includes two summary scores, one representing driving performance and one representing secondary-task performance. Driving performance was evaluated on a 1.3-mile test course, which included straight and curved road segments, a signalized intersection, a simulated work zone, two changeable-message signs, and six unexpected events. Secondary tasks included mental arithmetic, reading, writing, phone dialing, CD changing, route-guidance destination entry, eating, drinking and grooming. Twelve subjects drove an instrumented vehicle for 9 or 10 timed laps of the test course, each while performing a different secondary task or none (baseline). On average, we found a 15% decrement in driving performance scores on laps in which subjects engaged in a secondary task. Driving performance decrements were observed on 88% of these trials. Differences were observed between different secondary tasks. The pilot test results demonstrate the potential usefulness of the test protocol for assessing tradeoffs between primary and secondary tasks in driving.

Traffic information and some business models

In the era of ITS (intelligent transport systems), traffic information plays an important role in both urban location and travel choices. The e-business such as cyber shopping mall, location commerce, and mobile commerce will eventually make the traffic information more and more important and will be a good item to be treated as an object of business. This paper aims at an understanding the needs of traffic information and the emerging market opportunities for traditional transportation activities along with presentation of some business models. Worldwide, many ITS development and deployment programs deal with real-time traffic information that shows travel conditions on major freeways and arterials. These information services are viewed as key elements, necessary to the efficient management of urban traffic congestion. Although much emphasis has been placed on the improvement of traffic management systems with real-time traveler information, the effect of this on travelers and/or business is not well understood. These recent evolutions indicate that there are a growing number of private firms interested in traffic information technologies; a variety of dissemination methods have been explored, including radio and television broadcasts, changeable message signs and in-car devices. This suggests that the development of traffic information will provide business opportunities for new products and services in the traffic, information provision, traffic management and operations arenas. This paper focuses on some aspects of these emerging business opportunities: the technology trends having to do with the architecture of traffic management centers and the possibilities of integrating and disseminating traffic information to the end-user, and the activity of the industrial sector in designing, developing and deploying traveler information system with some business models initiated. Although this paper presents a comparative analysis of the current state of the art in advanced traveler information technology and its market potential, some issues including the traveler’s willingness to use traffic information services pre-trip and en-route should be addressed for further discussion.

Texas Driver Understanding of Abbreviations for Changeable Message Signs

Research was conducted as part of an ongoing project for the Texas Department of Transportation to evaluate the use of changeable message signs (CMSs) in Texas. The objective was to determine motorist understanding of abbreviations for use on CMSs. A human factors study was conducted in six locations in Texas. Participants were given a list of abbreviations and were asked to interpret the full words or phrases. The results identified 24 abbreviations that were understood at an acceptable level for use on CMSs in Texas; acceptability was based on a criterion of 85 percent or more of the participants’ correctly interpreting the word or phrase. Differences in study location comprehension levels were also examined. Twelve abbreviations were recommended for use only at particular locations on the basis of the varying comprehension levels among the six study locations. Abbreviations that were understood by less than 85 percent of the participants were not recommended for use in Texas.

Fatigue-Life Evaluation of Steel Post Structures. II: Experimentation

Changeable message signs (CMS) are supported by cantilevered, inverted L-shaped structural components composed of a vertical post and a horizontal mast arm. The high-cycle fatigue failure of one CMS structure in southern California led to a detailed analytical and experimental study of components of CMS structures. This paper reports the results of the experimental studies and presents recommendations for future CMS construction. A companion paper documents the results of the field studies and finite-element analysis of components of CMS structures. Six cantilever specimens were tested to failure: one as-built post (AB1); two retrofitted posts (GR1 and CIP1); and three mast arms (MA1, MA2, and MA3). The specimens were tested at a stress range of 691 MPa (101 ksi). The fatigue life of all six specimens exceeded the AASHTO design fatigue life of 400,000 cycles for a stress range of 69 MPa. Alternate construction details; improved welding, fabrication, and quality assurance/quality control practices; additional field and wind-tunnel testing; and further laboratory experimentation are recommended.