Objective

In the first year of this project, we intend to develop and test improved emergency warning lights (EWL) for work zone vehicles in order to improve visibility and conspicuity, and to reduce reaction times, for drivers approaching the work zone. There at present a ubiquity of flashing amber signals from multiple different sources in the work zone. This project aims to design, fabricate and test an EWL that will uniquely identify Caltrans maintenance vehicles and which will thus convey to the public the special hazardous nature of the portion of the highway where they are seen.

In the second and third years of this project, we intend to develop enhanced rear warning lights for shadow trucks (ST). An ST serves to protect the slow-moving vehicles it is following, and bears flashing lights to warn away closing traffic. We propose a refinement of the current state-of-the-art shadow truck light bar, and will examine the visual properties of our proposed improvement. A prototype will be delivered at the end of the first year. In the second year, the device will be installed on an ST, along with a radar- or laser-based threat detector, and a field operational test conducted.

Methodology

We plan to design an EWL in the shape of a solid truncated cone invested with a plurality of orange-emitting LEDs arranged in multiple tapered vertical stripes, which will be ignited in such a way as to be always visible whatever the direction of regard, and to incorporate discernible motion. To assist us in the design process, and to assess the effectiveness of our design, we will conduct laboratory tests in which we measure reaction time, and detection and identification thresholds for viewing the EWL. Conspicuity will be assessed by juxtaposing the EWL with other prominent visual elements in the scene. In the design process, observers will view a computer simulated display of an EWL, in which we can vary the presence of motion, spatial uncertainty, and/or distracting elements. We will then conduct additional tests on a prototype EWL built to our specifications. Our tests will evaluate the EWL under varying conditions of ambient illumination (time of day) and weather-related visibility.

Our refinement of the existing ST rear warning light will be a transformation of the current standard light bar into a motion-enhanced warning signal (MEWS). Detection and reaction time tests will be performed with observers viewing simulated signals displayed on a computer monitor under a variety of conditions, including day and night-time levels of ambient illumination, fixation either directly on the signal or to the side, and both optimal and faulty optical corrections (the latter inducing blur). We will then generate specifications for a prototype signal, approach a commercial partner for fabrication of the prototype, and evaluate the actual MEWS device under various conditions including outdoors with full sun.

We then intend to conduct a field operational test with the prototype warning signal installed on the rear of a Caltrans ST, and triggered by a radar- or laser-based threat detection device which will also serve to monitor and record vehicle behavior in order to assess the effectiveness of the MEWS signal.