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Pages 21-64

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From page 21...
... 21 Overview This chapter describes CMFs available in existing research that may be applicable to work zone safety analyses. The CMFs were first evaluated with respect to their potential reliability for work zone safety analyses.
From page 22...
... 22 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Feature Applicability toWork Zones Quality Facility Type Table Number Work zone with no lane closure Directly applicable High Freeways and expressways Table 7 Work zone with one or more lanes closed (workers present) Directly applicable High Freeways and expressways Table 8 Work at night (workers present)
From page 23...
... Catalog of Available Work Zone CMFs 23 should be checked before using these CMFs. There are no obvious reasons why these CMFs could not be applied in work zones; however, it is possible that some factors present in the work zone may not have been taken into account.
From page 24...
... 24 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook diaries from 64 freeway construction projects in four states (California, North Carolina, Ohio, and Washington) were analyzed (7)
From page 25...
... Catalog of Available Work Zone CMFs 25 Work Zone with One or More Lanes Closed (Workers Present) Description This CMF applies to work zones where at least one travel lane is closed and workers are present.
From page 26...
... 26 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Separate CMFs were developed for sites with lane closures and sites without lane closures. Again, the CMFs for night work at lane closures did not differentiate between the base number of lanes and the number of lanes closed.
From page 27...
... Catalog of Available Work Zone CMFs 27 CMFs Applicability to Work Zones: Directly applicable, data collected in work zones. CMFs are applicable to work zones with durations of between 16 and 714 days and lengths between 0.5 and 12.2 miles.
From page 28...
... 28 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Available CMFs Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source All All Not specified 696 to 124,907AADT .585* Not calculated (10)
From page 29...
... Catalog of Available Work Zone CMFs 29 Available CMFs Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source All Fatal, injury* All Not specified 0.83 0.01 (unadjusted)
From page 30...
... 30 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Available CMFs Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source All All Not specified Not specified 0.54 0.2 (4 ) Table 14.
From page 31...
... Catalog of Available Work Zone CMFs 31 developed with work zone data. The CMFs were developed using conditions that are likely to vary significantly from a work zone.
From page 32...
... 32 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook a work zone situation is unclear. These values should be used with caution.
From page 33...
... Catalog of Available Work Zone CMFs 33 2. For the Ullman et al.
From page 34...
... 34 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Change Median Width Description Medians serve to provide physical separation between opposing directions of traffic. Numerous studies have reported crash reductions due to the presence of medians (22, 24, 25, 26)
From page 35...
... Catalog of Available Work Zone CMFs 35 CMF Application Notes 1. The CMF values in Tables 19 and 20 were calculated by finding the inverse of CMF values for providing left turn lanes.
From page 36...
... 36 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook whereas the average median width for roads with partial or no access control ranged from 29 to 40 ft.
From page 37...
... Catalog of Available Work Zone CMFs 37 CMF Application Notes 1. The CMFs listed in Tables 21 and 22 were derived from past studies on non-work-zone roads, so their potential applicability to a work zone situation is unclear.
From page 38...
... 38 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Base Condition: For the first CMF, the base condition is a tangent section. For rural four-lane highways, the base condition is roadways with a maximum speed limit of 55 mph (31)
From page 39...
... Catalog of Available Work Zone CMFs 39 Available CMFs Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source 0.01 ≤ SV ≤ 0.02 All All Rural two-lane arterial Not specified 1+6*
From page 40...
... 40 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source All All Urban, four-leg signalized intersection 7,200 to 55,100 (major road AADT) 550 to 2,600 (minor road AADT)
From page 41...
... Catalog of Available Work Zone CMFs 41 Remove Right Turn Lane Description Removing right turn lanes from an intersection affects the safety and capacity of that facility. Currently, no CMF is available for removing right turn lanes; however, the HSM includes a CMF for providing right turn lanes.
From page 42...
... 42 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook CMF Application Notes 1. The CMF values listed in Tables 27 and 28 were calculated by taking the inverse of the CMF values for providing right turn lanes.
From page 43...
... Catalog of Available Work Zone CMFs 43 removing bicycle lanes, it is assumed that the effect of removing a bicycle lane is the inverse of providing one. CMFs Applicability to Work Zones: Possibly applicable.
From page 44...
... 44 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Available CMFs Crash Type Crash Severity Facility Type Range Volume Standard CMF Error Source All Rural two-lane arterial Not specified = proportion of driveway-related crashes = TWLTL-involved left turn crashes as a proportion of driveway- related crashes Not calculated (4 ) All All All Urban and rural two-lane road Not specified 1.25 (unadjusted)
From page 45...
... Catalog of Available Work Zone CMFs 45 Crash Type Severity Facility Crash Type Volume Range CMF Error SourceStandard Single vehicle run off road, multiple vehicle head-on, side swipe All Rural twolane roadway 400 to 2,000 AADT Not calculated (4 ) Single vehicle run off road, multiple vehicle head-on, side swipe All Rural two- lane roadway >2,000 AADT 1.05 Not calculated (4 )
From page 46...
... 46 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Crash Type Severity Facility Crash Type Volume Range CMF Error Source Standard Single vehicle run off road, multiple vehicle head-on, side swipe All Rural two- lane roadway <400 AADT 1.05 Not calculated (4 ) Single vehicle run off road, multiple vehicle head-on, side swipe All Rural two- lane roadway 400 to 2,000 AADT Not calculated (4 )
From page 47...
... Catalog of Available Work Zone CMFs 47 Reduce Shoulder Width Description Shoulder widths may also be reduced during work zone activities. The HSM considers a 6-ft-wide lane as the baseline value for two-lane and multilane roadways.
From page 48...
... 48 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Source Single vehicle run off road, multiple vehicle head-on, side swipe All Rural two-lane roadway, undivided multilane roadway <400 AADT 1.10 Not calculated (4 ) Single vehicle run off road, multiple vehicle head-on, side swipe All Rural two-lane roadway, undivided multilane roadway 400 to 2,000 AADT Not calculated (4 )
From page 49...
... Catalog of Available Work Zone CMFs 49 Available CMFs Crash Type All Crash Severity All Facility Type Rural two- lane road Volume Range Not specified CMF 1.04 Standard Error Not specified Source (4 ) Table 40.
From page 50...
... 50 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook 2. The CMF in Table 41 was developed using data from a single permanent site in Missouri using an empirical Bayes analysis.
From page 51...
... Catalog of Available Work Zone CMFs 51 lane length was accompanied by installation of barriers or other changes that might interact with the speed-change lane length, these CMFs should be used with extra caution. Base Condition: Freeways with ramp entrances/exits located on the right side of the road.
From page 52...
... 52 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook specify the magnitude of the sight distance change that occurred to generate the CMFs. The CMFs for reducing intersection sight distance were assumed to be the inverse of the CMFs for increasing the sight distance.
From page 53...
... Catalog of Available Work Zone CMFs 53 Figure 13. Typical freeway work zone crossover application from MUTCD (39)
From page 54...
... 54 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook CMFs Applicability to Work Zones: Directly applicable, data collected in work zones. Base Condition: Single lane closure in one direction.
From page 55...
... Catalog of Available Work Zone CMFs 55 CMFs Applicability to Work Zones: Possibly applicable. CMFs were not developed with work zone data, so caution should be used for work zone applications.
From page 56...
... 56 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Available CMFs Increase retroreflectivity of white edgeline, yellow edgeline, and yellow centerline Increase pavement marking retroreflectivity of white edge lines from X to Y mcd/m2/lux Increase pavement marking retroreflectivity of white skiplines from X to Y mcd/m2/lux Increase pavement marking retroreflectivity of yellow edge lines from X to Y mcd/m2/lux Increase pavement marking retroreflectivity of yellow centerlines from X to Y mcd/m2/lux Crash Type Several* All All All All All Crash Severity All All All All All All Facility Type Rural; multilane arterials and freeways Three-lane principal arterial Two-lane principal arterial Three-lane principal arterial Three-lane principal arterial Two-lane principal arterial Volume Range Not specified 2,752 to 47,572 2,752 to 47,572 2,752 to 47,572 2,752 to 47,572 2,752 to 47,572 Standard Error Not specified Not specified Not specified Not specified Not specified Not specified Source (43 )
From page 57...
... Catalog of Available Work Zone CMFs 57 slowing approach speeds, and it may improve driver expectations when approaching a work zone lane closure (44)
From page 58...
... 58 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook CMFs Applicability to Work Zones: Questionably applicable. CMFs were not developed with work zone data, so caution should be used for work zone applications.
From page 59...
... Catalog of Available Work Zone CMFs 59 zone environment. For example, the HSM CMFs assume a base case of no barrier being present.
From page 60...
... 60 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook 2. The barrier CMFs shown here also reflect results for cable barrier, guardrail, and bridge rail.
From page 61...
... Catalog of Available Work Zone CMFs 61 segment in Michigan without a work zone showed that drivers had a tendency to reduce their speed by as much as 5 mph as they approached the patrol car, but accelerated back to their original speed or higher (up to 3 mph) after passing it.
From page 62...
... 62 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook were significantly different between states with and without increased fines in work zones (3)
From page 63...
... Catalog of Available Work Zone CMFs 63 purchases. In 2013, a study in Saskatchewan conducted an advertisement effectiveness study to evaluate awareness of paid construction zone advertising, finding that 70% of the questionnaire respondents agreed that advertising messages have changed their behavior (56)
From page 64...
... 64 Estimating the Safety Effects of Work Zone Characteristics and Countermeasures: A Guidebook Other Reported Safety Impacts Strategies to enhance safety at work zone access and egress locations have been implemented by several agencies, but only a few studies have been conducted to quantify or qualify the results of those implementations. Regarding the use of enhanced temporary traffic control devices and ITS, an access and egress survey indicated that DOTs and contractors believed that improper use of traffic control equipment can be a major contributor to confusion for truck drivers, equipment operators, and the traveling public (69)

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