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21 two-way left turn lanes in the study sample were in the western region. The two-way left turn lanes did not account for the estimated West effect, however, since this estimate remained virtually unchanged when the data from the two-way left turn lane sites were deleted from the model. Table 3. Results for a marked crosswalk pedestrian crash model. Parameter Estimate S.E.* 95% Confidence Limits p-Value Intercept −15.09 1.65 (−18.33, −11.86) < .0001 Log (ADP) .33 .06 (.20, .45) < .0001 Log (ADT) .99 .17 (.65, 1.19) < .0001 Two lanes −.68 .26 (−1.19, -.18) .0074 Raised median −.58 .27 (−1.12, −.04) .0338 West region .77 .19 (.40, 1.14) < .0001 Dispersion 1.48 .41 (.85, 2.55) – *S.E. = Standard Error The North-South regional variable was not statistically significant. East-to-West effects were modeled as two variables, one comparing West to East, and the other comparing Midwest to East. The West-to-East comparison was significant, while the Midwest-to-East comparison was not. These variables were then collapsed to a single variable contrasting West with Midwest and East combined, which is the form used in the model of table 3. The apparent effect due to the western region was investigated further to see if this effect could be attributed to differing distributions of speed limits and/or numbers of lanes. This did not prove to be the case. Table 4 shows estimates of the same model parameters on the data subsets obtained by leaving out the data from each of the major cities. In general, the estimates are quite consistent across the subsets. All estimates listed were statistically significant at a .05 level with the exception of the two marked with an asterisk. These were the raised median effects on the datasets that omitted data from New Orleans, LA, and from Milwaukee, WI. The p-values for these estimates were .10 and .08, respectively. Results from the more detailed crash modeling on unmarked crosswalks are presented in tables 5 and 6. In contrast to the results of table 2, table 5 shows that when a variable indicating the presence of a median was included in the model, the effect of traffic volume (ADT) became statistically significant. As with marked crosswalks, various median types were also considered; in this case, a variable indicating a median of any type versus no median was the most relevant characterization. For unmarked crosswalks, the East, Midwest, and West comparisons showed the eastern region to have significantly lower crash rates than either the West or Midwest. Thus, a two-level variable contrasting east with the other two regions was used. The North-South comparison was again not significant. Table 4. Parameter estimates for marked subset models. Estimates on Subsets Parameters Seattle San Francisco Oakland New Orleans Milwaukee Cleveland Gainesville Cambridge Intercept −15.16 −15.22 −15.07 −14.91 −15.52 −14.97 −14.99 −15.54 Log (ADP) .32 .34 .36 .31 .34 .30 .34 .34 Log (ADT) 1.01 1.00 .97 .95 1.04 1.00 .98 1.05 Two lanes −.68 −.77 −.69 −.96 −.64 −.69 −.65 −.53 Raised median −.59 −.71 −.59 −.49* −.50* −.60 −.58 −.60 Western region .86 .75 .58 .87 .71 .77 .70 .70 *Not statistically significant at .05 level.