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20 In addition to the variables included in the models presented above, data were available for several other factors potentially associated with crosswalk safety. These included: • Speed limit. • Location of crosswalk (intersection or midblock). • Presence and type of median. • Type of crosswalk marking (marked only). Neither speed limit nor crosswalk location (intersection or midblock) had a significant effect in the models for marked or unmarked crosswalk crashes. Initially, three types of medians were compared with no median. These were: • Raised medians. • Painted medians. • Two-way left turn lanes. Several specific types of crosswalks were represented in the data, but the primary comparison came down to a comparison between the standard markings (two parallel lines) versus designs with more markings (e.g., continental or ladder patterns shown in figure 12). In attempting to estimate these more detailed models, it was also a concern to consider effects due to specific locations (i.e., cities, States, regions) from which the data were obtained since crashes, types of medians and crosswalks, and other variables were not uniformly distributed across these locations. To this end, two sets of regions were identified (North-South and East-Midwest-West), and class variables indicating these regions were included in the models. A second approach was to estimate a model using data from all locations, then to re-estimate the model while omitting the data from each of the eight cities where the most data had been obtained, one step at a time, to see how the estimates changed. These eight cities and the total number of observation sites at each are listed below. • Seattle, WA (204). • San Francisco, CA (182). • New Orleans, LA (160). • Milwaukee, WI (136). • Cleveland, OH (110). • Cambridge, MA (92). • Oakland, CA (90). • Gainesville, FL (90). A few iterations of this process resulted in a model for marked crosswalk crashes summarized in table 3. The model for table 3 contains no variable pertaining to crosswalk type, a single variable indicating a raised median as opposed to no median or another median type, and another variable indicating the western region of the country as opposed to the East or Midwest. In some preliminary models, there was an indication that the crosswalk types with more markings were associated with slightly lower crash rates than the standard type. These results were not consistent across models and became quite nonsignificant when regional variables were included. Similarly, preliminary models indicated that raised medians were marginally better (associated with lower crash rates) than crosswalks having no median or painted medians, while two-way left turn lanes were significantly worse than the other types. With the addition of the East-Midwest-West regional variables, the two-way left turn lane effect became nonsignificant, and the raised median effect became more significant. All of the