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7 curve TCDs are reported to be used more often than at the might reveal different patterns in driving habits or in how they county level. This is probably due to the fact that state roads respond either to TCDs or to the curves themselves. tend to have higher traffic volumes and are generally held to The first task was to convene focus groups of crash- a "higher standard" than are county roads and to the fact that involved and typical drivers. Two separate focus groups state road departments have more resources available to them. were held in East Lansing, Michigan, in March and June With regard to identifying curves that are difficult to sign 2004. The intent of the focus-group exercises was to discuss or cause problems for average drivers, there was some dis- TCDs used on rural, two-way, two-lane horizontal curves. agreement. State and county-level respondents tended to These sessions were spent discussing TCDs in general, iden- agree that the five most-difficult curves to sign are "broken- tifying actual problem curve situations encountered by the back" curves, curves that get sharper as the driver goes through participants, and then reviewing the TCDs that had been them, spiral curves, curves over the top of a hill, and back-to- deployed and how they might be modified to make the situ- back curves. However, they indicated that the five types of ations less problematic. There was also discussion about re- curves that are the most-difficult to drive are spiral curves, sponses to advisory speed signs and the general topic of TCDs curves over the top of a hill, unexpected curves, sharp curves for horizontal curves. after a long tangent, and very sharp curves. According to the As noted above, the initial goal had been to convene one respondents, curves that are most difficult for drivers to nego- focus group of around 10 drivers evenly split between those tiate are those that violate their expectations, that include a who had been involved in crashes on rural curves and "typi- combination of factors, or both. cal" or average drivers who had not been involved in that sort In conclusion, the state of the practice with respect to curve- of crash. Recruitment for the first exercise did not go accord- related TCDs on rural two-way, two-lane roads is consistent ing to plan, and a smaller group was used (five participants), in some aspects, but not in others. Both the focus groups and only one of whom was known to have crashed. While the the survey yielded similar results. Standards and methods cited potential crash-involved participants were identified using crash records, the relatively limited numbers made recruit- are relatively uniform, and variation in the standard infor- ment difficult. The non-crash participants were simply iden- mation that is used appears to be minor. From what the prac- tified using local and web-based telephone directories. As it titioners have stated, the standards are generally understood turned out, the smaller group was better for the type of activ- and followed in their jurisdiction, although "in-house" train- ities undertaken and allowed ample opportunity for discus- ing or practice sometimes overrides printed guidelines. Most sion and interaction by all participants. A second group of agencies feel that they have achieved consistency within six participants was convened later although it contained no their own jurisdiction, but are less positive about what is hap- pre-identified crash-involved participants. Participant ages pening elsewhere. State-level agencies were more confident were estimated to range from the early 20s to mid-70s with than were county-level agencies that curve signing and advi- five male and six female participants. All participants were sory speed determination practices were the same across their from suburban or rural areas in the three counties surround- jurisdiction. The biggest potential problem area appears to be ing the urban area of Lansing/East Lansing, Michigan. The in assessing and establishing advisory speeds. As a point of telephone recruiters who contacted potential participants interest, if the 2003 version of the MUTCD is followed, it can concentrated on exchanges from suburban and rural areas so be expected that there will be even more inconsistency among that there would be a good experiential base with rural roads jurisdictions and that drivers will see some curves undergo and curves. All participants had experience with both urban significant changes in the advisory speeds that are posted. The and rural streets and roads in the area. practitioners surveyed in this study seemed to all be of the In general the participants in both focus groups were same mind with respect to which curves are most difficult to knowledgeable about the typical TCDs used for rural curves. sign and drive. Better communication among agencies, either They indicated that they have lower expectations for the num- through state oversight or technology transfer programs, may ber of TCDs present on low-volume facilities. At some point, be needed to improve consistency. both groups indicated that there needs to be better mainte- nance of TCDs on rural curves, whether it is by re-striping edge lines or clearing brush around signs. In addition, the DRIVER FOCUS GROUPS participants commented that there is a need for better con- sistency among states and, more specifically, among counties The perceptions of drivers regarding the treatment of hori- in Michigan. zontal curves were also assessed. While information from In terms of the specific TCDs that participants think would drivers is useful in its own right, it is also useful to compare be helpful at curves, participants indicated their preference for their perceptions with the practitioners'. In addition to assess- ing driver perceptions, an attempt was made to differentiate Advance curve warning signs with advisory speed plates; between those who had been involved in a crash on a hori- Information (via signs) regarding other potential issues zontal curve and those who had not, the idea being that a com- at the curve such as an intersection on the curve or loose parison between curve-crash-involved and "typical" drivers gravel; and