The National Academies Press

Currently Skimming:

Pages 220-239

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 220... ... 220 This section describes various methods by which work zone strategies are evaluated. 13.1 Typical Work Zone Crash Characteristics Increased crash risks at a given work zone are a combination of temporary changes in geo metrics and influences related to work activity. Read the entire page →
From page 221... ... Framework for Evaluation of Work Zone Strategies 221 • Use of demandmanagement strategies to reduce volumes through work zones during the day. • Use of enhanced or automated traffic law enforcement (or both) Read the entire page →
From page 222... ... 222 Strategies for Work Zone Transportation Management Plans • Other explanatory factors after the work zone strategy deployment. Increased law enforce ment may cause drivers to reduce speed or be less aggressive, which potentially reduces crashes. Read the entire page →
From page 223... ... Framework for Evaluation of Work Zone Strategies 223 For example, a particular work zone is being assessed with the following values: C = 90 crashes over the past 1 year within this work zone, N = 1 year of data, V = 35,000 vpd, and L = 8 miles. The resulting segment crash rate (equation 2) Read the entire page →
From page 224... ... 224 Strategies for Work Zone Transportation Management Plans where CMFall = crash modification factor for all crash types and all severities in the work zone; and % increase in duration = the percentage change in the duration (days) of the work zone. Read the entire page →
From page 225... ... Framework for Evaluation of Work Zone Strategies 225 To compute the total number of crashes expected during a work zone, multiply the per mile number of crashes normally occurring on the roadway segment each year by the duration of the work zone and calculate the overall WZCMF for the AADT of the roadway segment. As Equation 6 shows, if a crash rate is used, then the rate is first multiplied by the length of the project. Read the entire page →
From page 226... ... 226 Strategies for Work Zone Transportation Management Plans 13.4.3 Example 1. Computing an Expected Crash Rate per Month during Construction A work zone engineer plans to monitor crashes occurring during a 2year, 5mi Interstate widening construction project. Read the entire page →
From page 227... ... Framework for Evaluation of Work Zone Strategies 227 If good non–work zone crash data are not available for the segment, then the work zone engineer can apply a previous work zone SPF for fourlane facilities (equation 11) Read the entire page →
From page 228... ... 228 Strategies for Work Zone Transportation Management Plans the work zone engineer may conclude that crashes were not excessive relative to expectations. The difference in results shown in Figure 13.2 using both methods is another reminder of the importance of engineering judgment when interpreting and using planninglevel estimates. Read the entire page →
From page 229... ... Framework for Evaluation of Work Zone Strategies 229 The total number of crashes expected for each alternative is calculated using the results of equation 13 as follows, assuming 24 months (Years 1 and 2 summed) for Alternative 1: ( ) Read the entire page →
From page 230... ... 230 Strategies for Work Zone Transportation Management Plans 13.5 Evaluation of Alternative Work Zone Design Using Alternative CMFs Work zone designers developing construction plans have options for accommodating traffic through the various phases or stages of the project. These alternatives can include factors such as whether to close lanes or shoulders, use narrower lanes, close ramps, reduce acceleration or deceleration lane lengths, and deploy together with various technologies (e.g., EQWSs, DLMs) Read the entire page →
From page 231... ... Framework for Evaluation of Work Zone Strategies 231 Work Zone Condition Work Zone Application CMF Volume Range Quality Crash Severity Stationary Police Enforcement DA 0.585 <125,000 M A Automated Speed Enforcement P 0.83 NS H F/I Speed Feedback Display P 0.54 NS H A Transverse Rumble Strips (Nighttime) (Queues Not Present/Queues Present) Read the entire page →
From page 232... ... 232 Strategies for Work Zone Transportation Management Plans Step 3. Obtain appropriate baseline crash estimate for applying CMFs. Read the entire page →
From page 233... ... Framework for Evaluation of Work Zone Strategies 233 and fatal crashes. Multiplying the appropriate CMF by the SPF provides an estimate of the crash frequencies expected on a given type of roadway for a given work zone condition. Read the entire page →
From page 234... ... 234 Strategies for Work Zone Transportation Management Plans work zone is introduced. Therefore, agencies might not measure strategies that attempt to affect tripmaking decisions and behaviors against what was happening before the work zone implementation, but instead measure relative to what would have occurred had the particular strategy not been implemented. Read the entire page →
From page 235... ... Framework for Evaluation of Work Zone Strategies 235 or the crash rate along a particular section of roadway, but the types of crashes occurring might be less severe. With respect to safety surrogate measures, these are highly site specific and best suited to evaluating strategies when a withoutwith comparison at each site can be made. Read the entire page →
From page 236... ... 236 Strategies for Work Zone Transportation Management Plans assessment on the conditions that the strategy attempts to target. Examples of data would be the dates of implementation of night or weekend work or the dates of a major phase change when a particular ramp was closed to traffic. Read the entire page →
From page 237... ... Framework for Evaluation of Work Zone Strategies 237 13.8.5 Productivity The productivity of work zone construction operations has definitions that range from how effective and safe workers are on the job to exact metrics of how many units of a construction product are accomplished in a certain span of time. The most widely accepted definition focuses on units produced over a defined time duration, or, conversely, on the labor hours needed to produce a unit. Read the entire page →
From page 238... ... 238 Strategies for Work Zone Transportation Management Plans Audiences for data and results can vary from projectlevel personnel, to districtlevel manage ment, to centraloffice management, to elected or appointed officials, to the traveling public. These different audiences will be interested in different levels of information. Read the entire page →
From page 239... ... Framework for Evaluation of Work Zone Strategies 239 Ullman, G Read the entire page →

From page 220...

... 220 This section describes various methods by which work zone strategies are evaluated. 13.1 Typical Work Zone Crash Characteristics Increased crash risks at a given work zone are a combination of temporary changes in geo metrics and influences related to work activity.