U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
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Field observations are conducted before and after deployment of countermeasures at site to obtain required data to derive the Measures of Effectiveness (MOEs). Data are collected to identify the effectiveness of the selected countermeasures at each site. Collected data include information pertaining to pedestrians and motorists. Different data collection strategies are used for intersections and mid-block locations. The observed pedestrian crossing behaviors at intersections are: crossing direction, crosswalk usage, pedestrians trapped in the middle of the street while crossing, crossing distance from the crosswalk (if not using crosswalk), waiting time before crossing, purpose of the trip, and yielding behavior. Similarly, the observed pedestrian crossing behaviors at mid-block locations are: crossing direction, trapped in the middle of the street while crossing, distance of crossing from the nearest intersection, waiting time for an acceptable gap, and yielding behavior. In general, the pedestrians’ activities approximately 200 feet on either side of the intersections are observed. At mid-block locations, pedestrians’ activities between intersections are observed. Data collected on motorists included traffic volume, vehicle approaching speed, yielding distance, etc. Data collection at a site depends on the countermeasures evaluated. Different types of data for evaluation of different countermeasures are listed in the following section.
1. Crash Frequency (Pedestrian Crashes/Year)
Crash data are collected from 1996 to 2000 within the Las Vegas metropolitan area. Based on this primary data, high crash locations in the Las Vegas metropolitan area are identified. Countermeasures are also selected based on the high crash locations as well as the type of crashes. The crash database includes pedestrian and vehicle crashes, excluding crashes in parking lots.
2. Crash Severity (Distribution of Crashes by Injury Type/Year)
The severity of crash data and their distribution within the Las Vegas metropolitan area are collected. In general, pedestrian crashes are divided into two categories: fatal and injury. Likewise, vehicle crashes are categorized as follows: fatal, injury, and property damage only (PDO). Specifically, crash severities are categorized on a 1 to 5 scale, where 1 is a crash with no injury and 5 is a fatal crash. Alternatively, the severity of crashes is divided into five categories as follows: fatal injury (K), incapacitating injury (A), non-incapacitating injury (B), no visible injury but complaint of pain (C), and no injury, property damage only (O), which is also referred as the KABCO injury scale.
3. Pedestrian and Vehicle Conflicts
A conflict involves an evasive action by a motorist or a pedestrian, where the vehicle and pedestrian are on a collision course. Evasive action is evidenced by a motorist stopping abruptly, slamming on the brakes, or swerving or by a pedestrian suddenly stepping back, lunging back, or running forward to avoid being struck by a vehicle. For a conflict to be scored, evasive action by either a motorist or a pedestrian need to be observed. At signalized intersections, only the pedestrians crossing between the stop bar and the intersection (including within the crosswalk) are considered for evaluating evasive action. Any conflicts occurring in a crosswalk at an intersection where countermeasures have been installed are recorded. At mid-block locations, all conflicts occurring within 300 feet upstream and downstream of the proposed crosswalk/countermeasure locations are recorded for both before and after deployment of the countermeasures. The pedestrian and vehicle conflict is expressed in terms of vehicle or pedestrian volume.
4. Percentage of Pedestrians who look for Vehicles before beginning to Cross
This MOE is scored if the pedestrians look in the direction of a potential threat before stepping off the curb onto the roadway. The data are reported as a percentage of the total pedestrians observed during the study period.
5. Percentage of Pedestrians who look for Vehicles before Crossing Second Half of the Street
This MOE is evaluated for the pedestrians who are at the centerline/center of roadway and visibly scan for vehicles before continuing to cross the second half of the street. The observed data are reported as a percentage of the total pedestrians observed during the study period.
6. Percentage of Captured Pedestrians
The percentage of captured pedestrians is the percentage of pedestrians who modified their paths to use a safety countermeasure, but who do not go out of their way to do so.
7. Percentage of Diverted Pedestrians
The percentage of diverted pedestrians is the percentage of pedestrians who modified their paths to use a safety countermeasure, and who went out of their way to do so. In this case, unlike “captured” pedestrians, these pedestrians would have to divert from their shortest path and walk some additional distance to use the safety countermeasure. This was determined based on observations of “back-tracking” movements by pedestrians.
8. Percentage of Pedestrians Who Pushed the Call Button
To record this MOE, every signal cycle for a given data collection period in which a pedestrian is present is observed as to whether or not the call button is pushed (cycles where no pedestrians are present are ignored in the percentage calculation). This MOE is recorded separately for each treated crosswalk at the intersection. Pedestrians are scored if they push the call button and the recorded data are converted to the percent of the total pedestrians crossing at a signalized intersection. Also, the percent of cycles where the call button is pushed is considered.
9. Pedestrian Not Completing Roadway Crossings
The data pertaining to pedestrians on the roadway or crosswalk can be divided into following categories:
9.1. Pedestrians in the Crosswalk during the Flashing DON’T WALK Phase
When crossing at a signalized intersection, pedestrians in the crosswalk at the end of the flashing DON’T WALK phase are those who are still in the roadway when the solid hand appears on the pedestrian signal. The corresponding percentage of total pedestrians crossing during the observation period is calculated. Data are collected from field observations.
9.2. Percentage of Pedestrians in the Crosswalk at the End of All-Red
The number of pedestrians in or near the crosswalk, who initiate their crossing before the solid DON’T WALK pedestrian signal who are still in a traffic lane after the cross street traffic receive the green signal, is counted. These data are reported in terms of the percentage of total observed pedestrians.
9.3. Percentage of Pedestrians Trapped in the Middle of Crossing
The number of pedestrians who are trapped in the middle of uncontrolled locations for at least 5 seconds is counted. This is generally the result of a pedestrian selecting a gap that is too small for them to completely cross the road before encountering approaching traffic. Pedestrians are scored as trapped in the middle at the centerline or between lanes if they have to wait to finish crossing. These pedestrians are converted into the percentage of total observed pedestrians.
10. Percentage of Pedestrians who begin their Crossing during WALK phase
This MOE is scored if a pedestrian steps from the curb into the crosswalk when the WALK signal is displayed on the pedestrian signal head. These data are converted into the percentage of total observed pedestrians.
11. Pedestrian Signal Violations (Crossing during the DON ’T WALK Phase)
A pedestrian is considered to be a signal violator if the pedestrian steps in or near the crosswalk from the curb when the solid DON’T WALK sign is displayed on the pedestrian signal head. Such violators are reported as a percentage of the total pedestrians observed during the study period.
12. Percentage of Drivers who Yielded to Pedestrians
Drivers’ yielding behavior to pedestrians is recorded. In particular, the yielding behavior of a motorist at a crosswalk, right-turning on red (RTOR), and yielding distance from the crosswalk is recorded. At signalized intersections, the percent of drivers who stop or slow to allow pedestrians to cross in front of them before proceeding is observed. Motorists’ yielding behavior is only scored when pedestrians have the right of way (i.e., during the WALK phase or during the flashing DON’T WALK phase if pedestrians started crossing when the WALK signal is displayed). At mid-block locations, it is the percentage of through vehicles that yields. Drivers’ yielding behavior is presented in terms of the percentage of the total observations. The collected data pertaining to motorists’ yielding behavior will be discussed next.
12.1. Distance Vehicle Yields before the Crosswalk
The distance a driver stops before a crosswalk at an intersection is the distance between the front bumper of the stopped vehicle and the marked crosswalk. The distance a turning driver (making a RTOR or a permissive left turn) stops/yields to pedestrians in the far crosswalks of an intersection (after initiating the turn and crossing the first crosswalk) is the distance between the front bumper of the vehicle and the marked crosswalk. The distance a driver yields at a mid-block crosswalk is the distance between the vehicle and the crosswalk when the driver first begins to brake in advance of the mid-block crossing. To score the distance the motorist yield to a pedestrian, both a vehicle and a crossing pedestrian need to be present at the same time. The yielding distance of the vehicles are recorded in three categories, less than 10 feet (<10 ft), between 10 to 20 feet (10-20 ft), and greater than 20 feet (>20 ft). To help with field observations, reference marks are identified on the curb at these intervals in advance of the crosswalk.
12.2. Percentage of Vehicles Blocking Crosswalk
The data for the frequency of vehicles blocking the crosswalk at the intersections and mid-block locations are collected. A vehicle is scored as "blocking the crosswalk” when it encroaches the crosswalk. These data on the vehicles that block the crosswalk are converted into the percentage of total observed vehicles during the study period.
12.3. Percentage of Drivers Turning Right on Red coming to a Complete Stop
Drivers are scored as coming to a complete stop if their wheels stopped turning before they enter the crosswalk. Drivers are scored as RTOR coming to rolling stop if the vehicles slow considerably, but the wheels do not stop turning before entering the crosswalk. If drivers turn without appreciably slowing, they are scored as RTOR without slowing. This MOE is reported in terms of the percentage of total observed vehicles during the study period.
At uncontrolled locations, a motorist is scored as yielding if he/she stops or slows, allowing the pedestrian to cross. A motorist is scored as unyielding if he or she passes in front of a pedestrian but would have been able to stop when the pedestrian arrive at the crosswalk. The problem requires calculating the distance that a motorist driving within the posted speed limit can stop for a traffic signal that changes to red using the signal-timing formula. This formula takes into account driver reaction time, safe deceleration rate, posted speed limit, and the grade of the road. The required distance for motorists to stop their vehicles safely within perception and break reaction time is called stopping sight distance (SSD). The SSD is the sum of the distance traveled during the brake reaction time and the distance to brake the vehicle to stop. According to American Association of State Highway and Transportation Officials (AASHTO), the SSD in meters is given as follows:
d = 0.278Vt + 0.039 V2/a meters (Equation 1)
Where,
t = brake reaction time, 2.5 sec;
V = design speed, km/h;
a = deceleration rate, 3.4 m/s2
Equation 1 is used to measure the distance beyond which a driver can safely stop for a pedestrian, and a mark can be placed at this distance on each side of the sidewalk. Motorists downstream of this marking after a pedestrian has entered the roadway can be scored as yielding to pedestrians, but not for failing to yield. Motorists upstream of the landmark when a pedestrian enter the crosswalk can be scored as yielding or not yielding because they have sufficient distance to safely stop. When a pedestrian first starts to cross, only drivers in the first half of the roadway are scored for yielding. Once the pedestrian approaches within half a lane of the marked median, the yielding behavior of motorists in the remaining lanes can be scored.
13. Pedestrian Delay
Pedestrian delay is the time a pedestrian has to wait before crossing the street at a marked or unmarked crosswalk. The duration starts when a pedestrian is first oriented to make the crossing and ends when they begin to cross. Pedestrian delays are measured using a stopwatch. At a signalized intersection, the stopwatch is started at the beginning of the flashing DON’T WALK phase. Each time a pedestrian arrives at a crossing area and prepares to cross the street, the time on the stopwatch is recorded for that pedestrian. When the WALK signal is displayed, the time appear on the stopwatch is recorded. The difference in time between the WALK signal display and the time each pedestrian spent waiting to cross the street is the individual pedestrian delay. The delay is averaged and reported based on the total observations. Pedestrian signal violators are not scored (i.e., pedestrians crossing during the flashing DON’T WALK or during the solid DON’T WALK phase).
When pedestrian crosses at a mid-block location, he/she may continue walking along the road/sidewalk (glancing over his/her shoulder) up until the time that a gap in traffic is detected and the crossing maneuver is initiated. In this case, a zero delay is recorded for the pedestrian, as the pedestrian continues to move up until the time of crossing. Pedestrian delay begins only when the pedestrian turns to initiate the crossing maneuver and stops walking to wait for a gap in traffic. If a pedestrian becomes delayed or trapped in the roadway after starting the crossing maneuver, this additional in-roadway delay is added to the delay the pedestrian experience before crossing to get the pedestrian’s total delay.
14. Vehicle Speed
Average vehicle speeds are measured using the space mean speed technique. A length of segment on the upstream of an intersection is measured and a corresponding time taken by a vehicle to travel this segment is recorded. The same strategy is used at mid-block locations. The mean and 85th percentile speed and standard deviation of speed are reported.
15. Vehicle Delay at Intersections/Mid-block Crossings
Vehicle delay is defined as an average amount of time a vehicle is stopped waiting at a traffic signal and/or yielding to a crossing pedestrian. The average vehicle stopped delay is measured using a delay study. Standard methodologies for conducting stopped delay studies at signalized intersections are used. The average vehicle stopped delay for an approach is reported.
16. Other Required Data
In order to quantify the MOEs, data pertaining to traffic volume, pedestrian volume, and crossing locations are collected. The required information and data collected are discussed next.
16.1. Vehicle Volume/Counts
The number of vehicles or vehicle counts is done during peak periods along the sites where countermeasures are deployed. Data are collected during morning and evening peak hours, 7:00 to 9:00 AM and 4:00 to 7:00 PM, respectively. Vehicle counts are obtained from video recording.
16.2. Pedestrian Volume/Counts
Pedestrian movements and pedestrian volume are obtained during peak hours for all the selected sites. Data are collected during morning and evening peak periods, 7:00 to 9:00 AM and 4:00 to 7:00 PM, respectively. At some of the locations, where the pedestrians’ peak volume need not be during the vehicle peak period, data was collected from 7:00 AM to 7:00 PM Pedestrian volume and movement information are obtained from real time field observations.
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