Traffic signs and signals

This Technical Summary pertains to Report 2023-26, “User-Centered Smart Traffic Sign Development Study,” published June 2023.

This flyer pertains to report 2016RIC10, Intersection Safety Technologies Guidebook.

This sample handout pertains to report 2014RIC20, Minnesota's Best Practices for Traffic Sign Maintenance/Management Handbook Including Insight on How to Remove Unnecessary and Ineffective Signage.

This sample handout pertains to report 2014RIC20, Minnesota's Best Practices for Traffic Sign Maintenance/Management Handbook Including Insight on How to Remove Unnecessary and Ineffective Signage.

Flaggers protect workers by providing temporary traffic control and maintaining traffic flow through a work zone. They are often the first line of defense to stop distracted, inattentive, or aggressive motorists from intruding into the work area. This project aims to develop an automated intrusion detection system to alert drivers who are unsafely approaching or entering a flagger-controlled work zone. A human factors user needs assessment found maintenance workers preferred a modified traffic signal to feature the alert system due to flagger risks of being in the roadway and drivers failing to stop and remain stopped when presented with the STOP side of the flagger sign. A modified traffic signal that could be operated using a handheld remote was developed. The low-cost embedded electronics on the traffic signal enabled it to track trajectories of nearby vehicles, detect potential intrusions, and trigger audio-visual warnings to alert the intruding driver. Usability testing in a simulated driving test found poor expectancies and stopping rates of the traffic signal-based alarm system compared to a traditional flagger but did demonstrate evidence that drivers may be less likely to stop and remain stopped with the flagger STOP sign than the red ball indicator of the traffic signal. Furthermore, some drivers corrected their initial stopping error after triggering the auditory alarm of the traffic signal. A follow up test found improved performance with the alert system incorporated into an audiovisual enhanced STOP/SLOW flagger paddle. Testing of the developed sensor system found the system capable of simultaneous multi-vehicle tracking (including estimation of vehicle position, velocity, and heading) with a range of up to 60 meters and angular azimuth range of 120 degrees and correctly detecting all test intruding vehicles.

This report discusses the development and implementation of new remote monitoring techniques to assist in the maintenance of modem traffic signals. Researchers developed and implemented algorithms for hardware fault detection, based on traffic flow analysis, in a software system. The system also analyzes maintenance information generated by the traffic signals, and correlated it with anomalies in traffic flow. The system's performance was tested by analyzing traffic flow during normal operation and during periods when hardware faults were deliberately injected into the system on a set of signals that the Minnesota Department of Transportation (Mn/DOT) generated. The results showed the following: • The traffic flow through signals does achieve a steady-state under various operating conditions. • Faults in the traffic signal hardware can be detected by monitoring the traffic flow rate. • Such a system can markedly reduce the time needed to process information generated by traffic signals' for maintenance purposes.

In a road research project, older drivers were asked to read street names as soon as they were able as they were approaching an intersection. The signs were always on the far sides of the intersection but could be either on the right or left side. Intersections of three levels of complexity were used. A repeated measures design was used. All main effects and all but one of the interactions were significant. The legibility distances obtained from 864 trials using 18 subjects showed that Diamond Grade and VIP Diamond Grade sheeting were equivalent but that both were significantly superior to High Intensity Grade sheeting which was in turn significantly superior to Engineering Grade. The differences among sheeting grades were more apparent at the more complex intersections. The viewing conditions on some of the streets resulted in reduced visibility and conspicuity causing markedly reduced legibility distances. There were no performance differences based on gender. The implications for driving safety were discussed in the context of visual information processing workload, divided attention and multitasking.

This work reports results of an experimental program on human factors issues in traffic signing. The first task examines the problems associated with the programming of signs for evaluation of driver response in simulation. It is concluded that growing technical tools permit traffic engineers to test proposed signage, and avenues of implementation are given. The second task examines driver response in simulation to multiple real-world signs. It is concluded that while much effort is given to distinguishing the utility of individual signs, multiple signs in combination produce more complex decrements. Recommendations are made as to maximum sign density. The final task provides an assessment of signage in future IVHS driving environments. It points to the role of signage as one component of communication. A list of issues for future signage implementation is given for consideration as the Department moves to provide safe and efficient transport for the people of Minnesota into the 21st century.

This report presents data using multiple-choice questionnaires to learn how drivers respond to traffic information in the form of advisory messages. Two experiments, comprising 112 participants, were conducted using the same technique and yielding similar results. The traffic information messages presented to participants varied in three respects; quantitativeness of information, imperativeness of advice, and timeliness of information. Two additional factors were examined; the amount of traffic congestion stated to be directly observable on the route and the stated accuracy of messages received in the past. Results obtained from the questionnaires indicate that the structure of the traffic message did influence the driver behavior. The propensity to depart from the planned route ahead of schedule was greater when respondents had; few exit options remaining, been told traffic levels were high, received accurate traffic information in the past, and had received messages which contained quantitative and/or imperative information. Traffic controllers with this knowledge of driver behavior could act to further reduce trip times and congestion by using the control tools currently available to them. The major conclusion we can draw from this study is that when possible and appropriate, advisory messages should contain accurate, timely, quantitative and imperative information.

This form letter was created as part of Report 2010RIC02, "Sign Retroreflectivity - A Minnesota Toolkit." It was created to be sent by other agencies as a follow-up to the County letter, to stress the importance of addressing FHWA requirements.