The National Academies Press

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Pages 248-263

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From page 248... ... 248 Introduction There is little research documented in the literature on the effect of work zone presence on urban street operation. Most of the research on the effect of work zone presence on operation has been conducted for freeways. Read the entire page →
From page 249... ... 249 four-lane arterial street. It was a short-term work zone that closed one lane and left one lane open for the subject direction of travel. Read the entire page →
From page 250... ... 250 zone was present. Each equation addressed different approach lane configurations at the intersection. Read the entire page →
From page 251... ... 251 long-term work zone has a lower capacity than a short-term work zone. The second trend in the values shown in Table J.4 relates to the change in capacity with number of lanes. Read the entire page →
From page 252... ... 252 Table J.5. Reported Capacity Values for Freeway Work Zones Source Lanes Open During Normal Operation Lanes Open During Work Zone Proportion Heavy Vehicles Work Zone Duration Measured Capacitya (vphpl) Read the entire page →
From page 253... ... 253 Table J.5. Reported Capacity Values for Freeway Work Zones Source Lanes Open During Normal Operation Lanes Open During Work Zone Proportion Heavy Vehicles Work Zone Duration Measured Capacitya (vphpl) Read the entire page →
From page 254... ... 254 = +fh 1.0 (J.3) long long longb I ( ) Read the entire page →
From page 255... ... 255 saturation flow rate estimate for a specific lane (or lane group) is highly dependent on the method used to aggregate the data that are recorded in each signal cycle. Read the entire page →
From page 256... ... 256 sites, this camera was located in the range of 300 to 500 ft upstream of the stop line. The second camera was mounted on a pole just behind the curb at the stop line and facing in a direction perpendicular to the flow of traffic on the subject approach. Read the entire page →
From page 257... ... 257 In addition to the data in the previous list, the data described in the following list were collected at each site that had a work zone present: • Weather condition; • Distance from start of work zone to stop line; • Distance from end of work zone to stop line; • Type of traffic control devices used to demarcate the work area; • Number of open lanes on the study approach; and • Number of work zone–related workers present. For each work zone study site, the technicians obtained (when available) Read the entire page →
From page 258... ... 258 to describe systematic variation in work zone saturation flow rate or capacity. The average values in the last row can be used to quantify the approximate effect of work zone presence on saturation flow rate. Read the entire page →
From page 259... ... 259 of the HCM2010 for heavy vehicles and right-turn vehicles as 2.0 and 1.18, respectively. These values can vary widely on a cycle-by-cycle basis depending on truck and turn vehicle presence. Read the entire page →
From page 260... ... 260 approach was used to control for other, unmeasured differences among sites. The work zone characteristics that were considered during model development included number of lanes after the work zone was removed, number of lanes when the work zone was present, approach width, work zone duration, and traffic control devices used to demarcate the work area. Read the entire page →
From page 261... ... 261 Table J.12. Model Statistical Description: Saturation Headway Adjustment Factors Model Statistic Value R2 0.81 Adjusted R2 0.73 Observations no Eight sites Calibrated Coefficient Values Variable Inferred Effect Value SD t-statistic bwz Adjustment factor for work zone presence 1.1654 0.0670 17.4 bwid Adjustment factor for work zone approach width -0.0057 0.0012 -4.9 breduce Adjustment factor for lane reduction at work zone 0.0402 0.0265 1.5 has three regression coefficients. Read the entire page →
From page 262... ... 262 where fwz = saturation flow rate adjustment factor for work zone presence; fwid = saturation flow rate adjustment factor for approach width; freduce = saturation flow rate adjustment factor for reducing lanes during work zone presence; aw = approach lane width during work zone (total width of all open left-turn, through, and right-turn lanes) , ft; no = number of left-turn and through lanes open during normal operation; and nwz = number of left-turn and through lanes open during work zone presence. Read the entire page →
From page 263... ... 263 Bonneson, J., B Nevers, J Read the entire page →

From page 248...

... 248 Introduction There is little research documented in the literature on the effect of work zone presence on urban street operation. Most of the research on the effect of work zone presence on operation has been conducted for freeways.