published_or_final_version / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 143-146).

The purpose of this paper is to analyze the performance of the Histograms of Oriented Gradients (HOG) as descriptors for traffic signs recognition. The test dataset consists of speed limit traffic signs because of their high inter-class similarities.   HOG features of speed limit signs, which were extracted from different traffic scenes, were computed and a Gentle AdaBoost classifier was invoked to evaluate the different features. The performance of HOG was tested with a dataset consisting of 1727 Swedish speed signs images. Different numbers of HOG features per descriptor, ranging from 36 features up 396 features, were computed for each traffic sign in the benchmark testing. The results show that HOG features perform high classification rate as the Gentle AdaBoost classification rate was 99.42%, and they are suitable to real time traffic sign recognition. However, it is found that changing the number of orientation bins has insignificant effect on the classification rate. In addition to this, HOG descriptors are not robust with respect to sign orientation.

A standardized color code is used to aid the driver in the prompt recognition of highway signs. At night, these signs are illuminated by various light sources including the headlights and other fixed light sources. These light sources may distort the appearance of the colors of the signs at night. The first objective of this study was to provide information about human capabilities with respect to the recognition of different colors under daytime and nighttime lighting. The second objective was to examine the effect of changing the specifications for highway colors from the Federal Highway Administration (FHWA) standards to the American National Standards (ANSI) safety color specifications. A laboratory experiment was conducted in which subjects named the perceived colors of retroreflective signs viewed under daytime and nighttime lighting. Forty subjects from four different age groups representing the driving population participated in the study. Three color samples (red, orange, and yellow) in three different grades (engineering grade, high intensity grade, and diamond grade), and two different color specifications (FHWA and ANSI) were used. Four different fixed light sources (clear mercury, coated mercury, coated metal halide, and high pressure sodium) were used for illuminating the signs. For the nighttime condition, two headlights were used (metal halide and tungsten halogen). Daytime lighting was simulated using a fluorescent D-65 light source. Response times as well as correct responses for naming the colors were collected for each subject. Significant differences were found for nighttime versus daytime viewing of the signing materials. In general, for nighttime viewing, red and orange colors were identified faster than yellow color samples. In most cases, FHWA colors were identified significantly more accurately and faster than the ANSI colors. The coated metal halide headlight performed better than the other fixed light sources. There was no significant difference found between the tungsten halogen and the metal halide headlights. / Graduation date: 1991

In this thesis, the author developed a retroreflective sheeting selection technique for traffic signs. Previous research was used to determine the luminance needed by drivers (demand luminance). The author used roadways scenarios to determine the amount of luminance the retroreflective sheeting on a sign would produce (supply luminance). A spreadsheet was developed to determine the performance of different retroreflective sheeting types by comparing the demand and supply luminance for specific roadway scenarios. Using the results of previous studies, three demand luminance levels were created: replacement, adequate, and desirable. The replacement level represents the level of luminance when a sign needs to be replaced and is 2.5 cd/m2. The adequate level is the recommended amount of luminance when installing new traffic signs and is 10 cd/m2. The desirable level is the approximate level when additional luminance has diminishing returns and is 30 cd/m2. Supply luminance on a specific traffic sign was determined by evaluating roadway geometries, sign placement, retroreflective sheeting type and vehicle data. The author reviewed roadway geometries in Texas to estimate typical number of lanes, shoulder widths and horizontal curvature in the US. Sign placement from the MUTCD determined the typical lateral placements, sign heights, and sign twists. Vehicle data included vehicle dimensions and headlamp type. Both the supply and demand luminance were determined for a specific viewing distance for a given scenario. The viewing distance is the distance a driver needs to read or recognize a sign to respond properly. In addition, the type of sign, alphanumeric or symbol, determined how this distance was calculated. The author developed four sign groups to calculate the distance required to read and respond to a traffic sign, including 1) Stop required, 2) Reduction in speed required, 3) Read the message provided, and 4) Change of lane required. For symbol signs, the minimum required visibility distance (MRVD) was determined for the sign group and for text signs, the viewing distance at a legibility index (LI) of 30 ft/in was found. At these distances, the author calculated the supply luminance and then compared it to the demand luminance levels to determine the performance level. The author developed the Retroreflective Sheeting Selection Spreadsheet (RSSS) to allow others to use the methodology presented in this thesis. RSSS allows users to input the roadway data, vehicle data, and sign data. RSSS takes this information and looks up the supply luminance for the scenario. RSSS then compares the supply luminance to the demand luminance levels and outputs the retroreflective sheeting performance level for the scenario.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on Jan. 7, 2010. Major professor: Helen Yu. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Electrical Engineering." "2009." Includes bibliographical references (p. 82-83).

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