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Table 2 Accuracy Differences at Different Experimental Levels

Table 2
Accuracy Differences at Different Experimental Levels

Experiment Environment Inventory Element For all elements Overall
Lane width Sign width Sign lateral placement Driveway width Street light spacing Barrier height Sign height Sign support height Side slope
Experiment 1 Two-lane rural VMMS1 * * VMMS1 — * * VMMS1 * VMMS1 M* 
Rural interstate VMMS1 VMMSI M — — * * * * VMMS1*
Urban VMMS1 M M VMMS1 VMMS1 — * *   M*
Experiment 2   Two-lane rural * * * * — * * * * VMMS2* M* 
Rural interstate * * * — — * * * * VMMS2*
Urban * * * * * — * * — M*
Experiment 3 Two-lane rural * * * — — — * * — M M* 
Rural interstate * * * — — — * * — VMMS3*
Urban * * * — — — * *   M*
Experiment 4   Two-lane rural VMMS4 — M M — — — — — M* M* 
Rural interstate *  † — M — — — — — — M*
Urban VMMS4 — M VMMS4 VMMS4 — — — — M*

Table legend
— = Not tested
* = Not statistically different at the 95% confidence level
M = Data collected by the manual method are statistically more accurate at the 95% confidence level
VMMS1, VMMS2, VMMS3, VMMS4 = Data collected by the particular method are statistically more accurate at the 95% confidence level
† = Shoulder width measured in place of lane width