Potential MUTCD Criteria for Selecting the Type of Control for Unsignalized Intersections (2015) / Chapter Skim
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22 CHAPTER 3: LITERATURE REVIEW BACKGROUND The literature review task was subdivided into the following focus areas: Key reference documents, including the TRB HCM (23) , American Association of State Highway and Transportation Officials (AASHTO)
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23 The HCM defines LOS by computing or measuring control delay for each movement. These delays are based on the priorities of the traffic streams at the intersection, considering the traffic control devices as applied (or proposed)
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a Roundabo Source: Ad converted t of daily. Tw Figu SPFs and arterials: Three Three Four FourOther typ by the HS Determin of severa severity.
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25 Crash Modification Factor A CMF is a multiplicative factor used to compute the expected number of crashes after implementing a given countermeasure at a specific site. The CMFs currently in the HSM for stop-controlled urban and suburban arterials are intersection left-turn lanes, intersection rightturn lanes, and lighting.
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26 Table 7. Crash Modification Factors from Clearinghouse (29)
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27 in residential neighborhoods was an effective measure for reducing both the frequency and severity of collisions in urban areas. A later paper (31)
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28 data from three previous safety studies in San Francisco, Philadelphia, and Michigan and added a new data set from Toronto, Canada. Intersections were converted from either two-way stop control or one-way streets to all-way stop control.
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29 effective when approach volumes are unbalanced as when they are equal on all approaches. For rear-end crashes, which make up a small percentage of total crashes, the effectiveness decreases as total entering volumes increase and as the minor road volume drops below 25 percent.
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30 TWSC to AWSC to be about 47 to 64 percent, and they include references to the 2000 Harwood et al. study (43)
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31 Table 8. LOS for Two-Way Stop-Controlled Intersections Developed Using Simulation (48)
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32 stop control) in terms of intersection operation costs.
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Roadway Classifica Major Local Local Collector Collector Collector Collector a The tabl during the b Collision on the low c Approac d None m hour. A 1997 I hour inte delay, an HCM me all appro overall in for TWS the split b and the m pedestria Table 11 tiona Minor Local Local Local Local Collector Collector e is only appli peak hour.
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Figure 5 Figure Another performa selection (CORSIM character vehicle w combinat right)
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were run stop is pr increases point wh point is t show the Figure A 2008 s Highway 5,000 cas methodo The study choice of 10 percen recomme The auth is found t minor str streets se should be , resulting in eferred at lo , delay valu ere either co ermed the tr transition p 7. Major S tudy (56)
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Figure 8 In 2012, with the performa and left-t 5, 10, 15 roundabo was prod intersecti A numbe TWSC an Some of length ca NCHRP improvem models to step-wise modes at the LOS movemen delay and Figure 10 effectiven . Comparis Jiang et al.
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Figure 9 Fi . Intersectio gure 10.
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38 In a 2000 paper, Wu (58) discusses a new capacity analysis methodology based on the additional-conflict-flow method (developed from graph theory)
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evaluatio operation appropria typical de SELECT CROSSI 2009 Ma Figure 11 based on develope NCHRP NCHRP crossing to check 20 pedes exceeds 3 (rather th extension Traffic si NCHRP n and conce al efficiency te and prop signs. ING TRAF NGS nual on Un shows part major-stree d based upo Figure 11 Report 562 Report 562/ treatments.
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considere pedestria Cross signs Enha locati categ Activ displa Red: beaco Signa The guid appropria crossing spreadsh location. Figu City of T The City pedestria their PHB priority e based on d; otherwis n delay.
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41 City of Phoenix The City of Phoenix, Arizona, (64) adopted guidelines similar to Tucson's for installation of PHBs.
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42 Table 12. Arizona DOT PHB Evaluation Draft Guidelines (65)
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the Bould threshold The city on the pr state that both high be an inc In these c crosswalk pedestria been prep a similar T Minimum 20 peds pe 18 peds pe 15 peds pe 10 school * Young, e *
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44 At least 20 pedestrians crossing in the highest hour and, There is a marked crosswalk existing or justified at the location and, Other applicable pedestrian options have been reviewed and determined by engineering judgment to not be applicable. Pedestrian counts, a crossing gap study, and other key pieces of data must be obtained before and after installation.
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45 The posted speed limit is 40 mph or less (does not include school speed zones)
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