Yellow Transition Lane Control Signal Symbols for Freeway Traffic Management (FHWA/TX-97/1498-3F)

This report documents the research performed to assess the effectiveness and applicability of yellow diagonal and downward arrows for freeway traffic management purposes. Researchers examined motorist understanding of and perceived usefulness of the arrows through surveys of San Antonio motorists where these indications are being utilized as part of the TransGuide system. These results were compared to similar data obtained from motorists in Fort Worth where TxDOT operates a traffic management system utilizing a yellow X. Researchers also interviewed operators of the TransGuide system to assess their opinions of the yellow arrow indications, and to identify any difficulties they have experienced in utilizing these symbols in their daily traffic management activities. Finally, researchers performed a series of field studies to assess how drivers respond to yellow diagonal arrows and yellow Xs used to transition between a lane open and a lane closed condition.|Data collected through this research effort indicates that the use of both the yellow diagonal and downward arrows for freeway traffic management purposes are perceived positively by TransGuide system operators and the motoring public. Furthermore, no evidence of operational problems or difficulties due to the use of either of these non-standard symbols has been collected through field studies in San Antonio. Similar statements can be made concerning the yellow X. Motorists in Fort Worth rate this symbol fairly highly once they see it used in a freeway driving situation. Field studies suggest that the number of drivers exiting a closed lane when first encountering the yellow X symbol equals or exceeds those who would exit for the yellow diagonal arrow.