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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-05-7859 |
| Date | 2010 May 1900 |
| Creators | Paulus, Susan C. |
| Contributors | Hawkins, Harvey G. |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | application/pdf |
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