9_22_11_EB_state_exs - Compare Classic w/ Rate Control OBi...

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CE4001 Transportation Safety 1 Compare Classic w/ Rate Control S K XA OBi * Vi Vi XS K XS OBRi 2 1 5 . 0
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CE4001 Transportation Safety 2 Empirical Bayesian Method Based on conditional probability, or compute posterior based on prior i.e. the probability that something is true given the knowledge that something else has occurred.
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CE4001 Transportation Safety 3 Assuming use of the total entering volume for an I/S to compute an overall intersection crash rate is not logical Why not? e.g. compare 2 I/S I/S 1. high percentage of through traffic I/S 2. high percentage of left turning traffic Empirical Bayesian Method
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CE4001 Transportation Safety 4 Assuming use of the total entering volume for an I/S to compute an overall intersection crash rate is not logical Why not? Since left turn movement might result in accidents more often, I/S 2 will be ranked higher than I/S 1 But I/S 2 might be comparable to other left turn locations Empirical Bayesian Method
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CE4001 Transportation Safety 5 Bayesian method divides crashes patterns at an intersection into 15 different vehicle pair movements. For example, popular patterns for crashes: 1. Rear-end pre-stop line 2. Rear-end post-stop line 4. Right angle through’s 6. Left turn with opposing through Empirical Bayesian Method
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CE4001 Transportation Safety 6 Empirical Bayesian Equation Coefficients (Hauer 1988, Toronto) Pattern Model Form Coefficient bo b2 1 RRpre E{m}=bo*F 0.2052x10 -6 N/A 2 RRpost E{m}=bo*F 0.1014x10 -6 N/A 4 RAth E{m}=bo*F 2 b2 8.1296x10 -6 0.3662 6 LToppth E{m}=bo*F*F 3 b2 0.0418x10 -6 0.4634
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CE4001 Transportation Safety 7 Table shows E{m}, or the expected mean number of crashes per hour for each pattern F is the primary direction flow (primary through) F2 is the secondary direction flow (right angle through) F3 is the tertiary direction flow (opposing left turn) Pattern Model Form Coefficient bo b2 1 RRpre E{m}=bo*F 0.2052x10 -6 N/A 2 RRpost E{m}=bo*F 0.1014x10 -6 N/A 4 RAth E{m}=bo*F 2 b2 8.1296x10 -6 0.3662 6 LToppth E{m}=bo*F*F 3 b2 0.0418x10 -6 0.4634
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CE4001 Transportation Safety 8 EB Methodology: 1. Compute expected mean number of crashes, E{m} for each pattern. 2. Sum all E{m} for the entire
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This note was uploaded on 10/26/2011 for the course ECON 101 taught by Professor Dr.siam during the Spring '11 term at American University of Kuwait.

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9_22_11_EB_state_exs - Compare Classic w/ Rate Control OBi...

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