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From page 45... ... 45 5.1 Case Study Introduction One of the more common challenges related to access management on crossroads in the vicinity of freeway interchanges involves commercial development with high driveway density. These locations attract drivers who stop for fuel, food, lodging, or other travel-related amenities. Read the entire page →
From page 46... ... 46 Access Management in the Vicinity of Interchanges 5.2 Case Study Procedures and Assumptions The case studies summarized in this chapter are based on actual locations; however, some site characteristics have been modified to help demonstrate unique access management considerations. The content of each case study is structured to include the following elements: • Principle illustrated. Read the entire page →
From page 47... ... Case Studies 47 5.3.1 Case Study #1: Diamond Interchange with Signalized Terminal Intersection (without channelized right turn) Principle Illustrated • Show effects of restricting left turns by constructing a continuous, non-traversable median along the crossroad corridor. Read the entire page →
From page 48... ... 48 Access Management in the Vicinity of Interchanges Quantitative Operational Assessment. Based on the assessment methodology presented in Chapter 4, the average operating speed for both directions of travel is approximately 20 mph (recall the posted speed limit is 45 mph along this corridor) Read the entire page →
From page 49... ... Case Studies 49 Figure 5-3. Case Study #1 estimated operating speeds. Read the entire page →
From page 50... ... 50 Access Management in the Vicinity of Interchanges Quantitative Safety Assessment. The predicted six-lane arterial safety performance can be estimated by using the spreadsheet tool developed for NCHRP Project 17-58, "Safety Prediction Models for Six-Lane and One-Way Urban and Suburban Arterials." This tool is expected to be provided as a companion resource for the second edition of the HSM. Read the entire page →
From page 51... ... Case Studies 51 Overview of Possible Improvements Many of the collisions in this corridor appear to be related to left-turn ingress or egress. Two remedies for further investigation include the following: 1. Read the entire page →
From page 52... ... 52 Access Management in the Vicinity of Interchanges Site Conditions Figure 5-6 shows the east-west crossroad, with the freeway to the right or east side (just beyond view of the picture) Read the entire page →
From page 53... ... Case Studies 53 Quantitative Operational Assessment. The Chapter 4 operational assessment methodology, when applied to this case study corridor, results in an average two-way operating speed of 24 mph (posted speed limit is 35 mph) Read the entire page →
From page 54... ... 54 Access Management in the Vicinity of Interchanges the vicinity of the interchange terminal intersection immediately west of the on-ramp. Based on this and similar crash history at the case study location, it is apparent that the majority of crashes along this crossroad corridor are angle or rear-end collisions. Read the entire page →
From page 55... ... Case Studies 55 been locally calibrated. The use of the uncalibrated HSM models is suitable for assessing the approximate range of the crashes. Read the entire page →
From page 56... ... 56 Access Management in the Vicinity of Interchanges These four basic countermeasures would help enhance crossroad operations, but a second and more important question is if the number of crashes can be further reduced to enhance corridor safety. Based on the arterial safety performance functions provided in the 2010 HSM, the predicted number of crashes with a TWLTL can be directly compared to the predicted number of crashes for a four-lane arterial with a non-traversable median. Read the entire page →
From page 57... ... Case Studies 57 Site Conditions Figure 5-11 shows the east-west crossroad with the freeway to the right or east side (beyond view in the aerial) Read the entire page →
From page 58... ... 58 Access Management in the Vicinity of Interchanges Operational Evaluation Qualitative Operational Assessment. Upon inspection of the study corridor, it is apparent that the location is in a region that is developing. Read the entire page →
From page 59... ... Case Studies 59 Crash Description Average Number of Observed Segment Crashes (Year 1 to Year 3) Predicted Number of Segment Crashes Based on HSM Models (no calibration) Read the entire page →
From page 60... ... 60 Access Management in the Vicinity of Interchanges Overview of Possible Improvements At this location, there are no existing access control measures currently in use. See Figure 5-15. Read the entire page →
From page 61... ... Case Studies 61 Site Conditions Single-point urban interchanges (SPUI) are used primarily in built-up urban areas due to their small lateral footprint along the crossroad when compared to conventional diamond interchanges. Read the entire page →
From page 62... ... 62 Access Management in the Vicinity of Interchanges Operational Evaluation Qualitative Operational Assessment. The crossroad corridor is located in a maturely developed urban region. Read the entire page →
From page 63... ... Case Studies 63 Figure 5-17. Case Study #4 estimated operating speeds. Read the entire page →
From page 64... ... 64 Access Management in the Vicinity of Interchanges median. The HSM methods indicate that only one segment crash could be estimated in a period of 3 years if a raised median is constructed. Read the entire page →
From page 65... ... Case Studies 65 signalized U-turn or roundabout and return to the intersection where they could make a right turn -- the equivalent of a direct left turn. This form of an alternative or innovative intersection could significantly reduce the length of a queue and the time a queue would exist. Read the entire page →
From page 66... ... 66 Access Management in the Vicinity of Interchanges Site Conditions Figure 5-21 displays the Case Study #5 roadway. This road segment is positioned on the west side of a PARCLO. Read the entire page →
From page 67... ... Case Studies 67 a bank, a restaurant, and a big box store share the sole driveway along the south side of the segment. Along the north side, three separate tracts have two drives each. Read the entire page →
From page 68... ... 68 Access Management in the Vicinity of Interchanges Safety Evaluation Qualitative Safety Assessment. The crash diagram depicted in Figure 5-24 contains two clusters of crashes: one near the signalized intersection at the left or west edge of the diagram and another near the overlapping intersection areas of the southbound exit ramp and Street H with the subject crossroad. Read the entire page →
From page 69... ... Case Studies 69 Overview of Possible Improvements The collision pattern calls for treatments to reduce or eliminate angle conflicts between westbound vehicles and vehicles to and from tracts on the north side. The following items are intended to attack the problem. Read the entire page →

From page 45...

... 45 5.1 Case Study Introduction One of the more common challenges related to access management on crossroads in the vicinity of freeway interchanges involves commercial development with high driveway density. These locations attract drivers who stop for fuel, food, lodging, or other travel-related amenities.