An evaluation of guide signing at right multilane freeway exits with optional lanes

Abstract

In urban areas, complex geometric situations make the guide signing task difficult. Since only a limited amount of space can be devoted to guide signing information, careful consideration must be given to the content of each sign. Guide signs should contain enough information to clearly convey upcoming interchange geometry, but not so much as to overload the driver's ability to process information. Previous studies have identified improving communication of the optional lane situation at a multilane exit as an area for further research. The lack of explicit instruction in the MUTCD on how to sign multilane interchanges has led to diverse, non-uniform guide signing applications around the nation. A review of nationwide practices as part of this research found that guide signing treatments are different between and within many states. The Texas Manual on Uniform Traffic Control Devices explicitly recommends signs for multilane exits. This research tested guide signing alternatives to better communicate the optional lane situation. One alternative included use of the phrase "MAY EXIT" to help communicate the optional lane. In addition, alternatives using diagonal arrows over the optional lane were also tested. Finally, forms of pull-thru signing were tested to see if they were of benefit in helping communicate the optional lane. The alternatives were tested against the current method of signing to determine if increased driver comprehension could be realized through the use of the alternative signs. The results of the laboratory experiment showed that marginal improvements in comprehension resulted from the use of alternative guide signs. Recommendations were made as to the use of freeway guide signs, and further areas of research were identified.