Salt 2014 Salt Lake City TACT Enforcement Evaluation Report

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SALT LAKE CITY TACT EVALUATION September 25, 2014


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Salt Lake City TACT Evaluation Report
The goal of the SLC TACT project is to reduce unsafe behaviors and decrease crashes between
passenger and commercial vehicles. The SLC TACT intervention consisted of concentrated
media and increased enforcement over a three week period in April 2014 to encourage passenger
and commercial vehicle drivers to travel safely around one another within the city limits. Based
on data analyzed during Phase I of the project, the SLC TACT intervention focused on four
targeted behaviors for drivers of both passenger and commercial vehicles: 1) failing to yield the
right-of-way, 2) disregarding traffic signals, 3) improper turn, and 4) following too closely. The
evaluation of the media efforts are detailed in a different report.

This report concentrates on the evaluation of driver behaviors using observational, citations for
the targeted behaviors, and motor vehicle crash data. Below we describe the purpose, data, and
the key findings for each of the three areas.

Observational Data
Purpose: To directly assess driving behaviors pre and post the TACT intervention, we collected
information on the frequency of negative interactions occur between passenger and commercial
vehicles in Salt Lake City pre and post the TACT enforcement period.
Data Collection: Trained observers, using a standardized data collection form, collected data on
negative passenger and commercial vehicle driver interactions at designated intersections in Salt
Lake City. We collected data 3 weeks prior to the TACT enforcement period and 3 weeks post
TACT enforcement. All observers received classroom and field training (Please see Appendix 1
for the observational data collection protocol). We selected the intersections according to data
received from Salt Lake City Police Department and Utah Department of Transportation. These
sites were determined to have a high rate of commercial vehicle travel and passenger and
commercial vehicle crashes, while also providing a safe location from which to accurately
observe commercial and passenger driver interactions.

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The sites selected were
• 21South /9West-observations will occur at a large intersection with nearby truck stop
• 21South /7East-observations will occur at an intersection and mid-block locations
• 6North/4West- observations will occur at an intersection and mid-block locations
Because some of the targeted interactions (e.g., disregarding traffic signals and improper turns)
were more likely to occur at an intersection, while other interactions (e.g., following too closely)
were more likely to occur mid-block, observations were collected from both types of locations.
Mid-block observations were not conducted at the 21 South/9 West location due to a
combination of construction and a lack of safe observation locations.
Key Findings: As seen in Table 1, we conducted 48-observation shifts pre-enforcement and 67-
post enforcement. While the number of observation shifts differed between the time periods,
there was no difference between the rate of commercial vehicles observed per shift between the
pre- and post-enforcement periods (83 vs. 84, p =0.953). Please see Appendix 2 for commercial
vehicle counts by location.
Table 1. SLC TACT Observational Commercial Vehicle Count Pre- and Post- TACT
Enforcement
Observation Period

Pre-
Enforcement
Post-
Enforcement
Pooled T-test
P-value
Commercial Vehicle Count
Number of Observation Shifts 48 67
Sum 3990 5630
Mean (SD) 83 (81.9) 84 (80.4) 0.953
SALT LAKE CITY TACT EVALUATION September 25, 2014


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Below is a comparison of the rate of observed negative interactions by vehicle type pre and post
TACT Enforcement by location. Table 2 shows the rate of overall total negative interactions
decreased by almost half after the TACT intervention. The largest decrease was seen in
following too close and improper turns for both commercial and passenger vehicle drivers. This
same pattern was observed at each location.

Table 2. SLC TACT Negative Interaction Rate by Vehicle Type from
Observational Data Collected Pre- and Post-TACT Enforcement Period
Commercial Vehicles Passenger Vehicles
Interaction Type Pre Post Diff Pre Post Diff
Al l Locations
Total Interactions 2.31 1.30 -1.01
1
1.96 0.58 -1.38
1

Disregarding Traffic Signals 0.81 0.69 -0.13 0.29 0.16 -0.13
Improper Turns 0.56 0.19 -0.37 0.19 0.00 -0.19
Failure to Yield 0.21 0.10 -0.10 0.06 0.03 -0.03
Following Too Close 0.54 0.27 -0.27 1.40 0.31 -1.08
1

Other 0.19 0.04 -0.14 0.02 0.07 0.05
2100 S 900 W
Total Interactions 1.83 0.90 -0.94
1
1.56 0.36 -1.20
1

Disregarding Traffic Signals 0.63 0.52 -0.10 0.29 0.10 -0.19
Improper Turns 0.52 0.13 -0.39
1
0.19 0.00 -0.19
Failure to Yield 0.13 0.07 -0.05 0.04 0.01 -0.03
Following Too Close 0.44 0.13 -0.30 1.02 0.19 -0.83
1

Other 0.13 0.03 -0.10 0.02 0.04 0.02
2100 S 700 E
Total Interactions 0.13 0.07 -0.05 0.19 0.03 -0.16
Disregarding Traffic Signals 0.04 0.03 -0.01 0.00 0.01 0.01
Improper Turns 0.02 0.01 -0.01 - - -
Following Too Close 0.02 0.03 0.01 0.19 0.01 -0.17
Other 0.04 0.00 -0.04 - - -
SALT LAKE CITY TACT EVALUATION September 25, 2014


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Table 2. SLC TACT Negative Interaction Rate by Vehicle Type from
Observational Data Collected Pre- and Post-TACT Enforcement Period
Commercial Vehicles Passenger Vehicles
Interaction Type Pre Post Diff Pre Post Diff
600 N 400 W
Total Interactions 0.35 0.33 -0.03 0.21 0.19 -0.01
Disregarding Traffic Signals 0.15 0.13 -0.01 0.00 0.04 0.04
Improper Turns 0.02 0.04 0.02 - - -
Failure to Yield 0.08 0.03 -0.05 0.02 0.01 -0.01
Following Too Close 0.08 0.10 0.02 0.19 0.10 -0.08
Other 0.02 0.01 -0.01 0.00 0.03 0.03
1
Significant reduction in negative interactions (p < 0.05).
Rates are calculated as Negative Interactions observed per Observation Shift

The observational data show that there was a significant reduction between the rate of negative
interactions at each location between the pre- and post-TACT intervention time periods. The
greatest decrease was observed in the rate of following too close. The decrease in the rate of total
negative interactions following the TACT enforcement period suggests that the TACT
intervention positively affected driver behavior.
Targeted Behavior-Related Citations
Purpose: To assess the results of increased high visibility and awareness of the TACT
enforcement, daily counts of citations and warnings for the target behavior categories were
analyzed. A combined high visibility enforcement and awareness campaign was used alert the
public of the importance of decreasing risky driving practices around commercial vehicles.
Police officers reinforced the media messages with targeted enforcement and increased warnings
to passenger and commercial vehicle drivers when any of the four-targeted behaviors were
observed during the intervention period.
SALT LAKE CITY TACT EVALUATION September 25, 2014


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Data Collection: Citation data were obtained from two sources. Citations data for the four-
targeted behaviors from the Salt Lake City Police Department Record Management System for
the years 2012-2014 are presented in Figure 1. Comparing data from the same time period from
previous years allowed us to control for any temporal trends that may exist outside of the TACT
intervention. Data for Figure 2 were obtained from the Salt Lake City Police Traffic
Enforcement Section. This section tracked the citations and warnings issued during the TACT
enforcement period.
Key Findings: Figure 1 shows the comparison of citations issued by day for the first six months
of the years 2012 to 2014. The high visibility enforcement period is delineated with vertical bars
so that the rates between the pre-enforcement, enforcement, and post-enforcement periods can be
compared across years. We found that citations remained relatively constant over the six month
time period with more citations issued in 2012 compared to 2013 and 2014. The data for the
TACT enforcement period in 2014 shows an increase in the number of citations issued at the end
of the enforcement period. Because the high visibility campaign involved both issuing citations
and warnings, we obtained data from the Salt Lake City Traffic Enforcement Unit, which tracks
both of these activities.


SALT LAKE CITY TACT EVALUATION September 25, 2014


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Figure 2 shows that there was sustained enforcement throughout the TACT period (showing
there were 40 to 50 warnings and citations issued per day) with police officers issuing more
warnings than citations in the beginning of the time period with a reversal at the end of the
period.

SALT LAKE CITY TACT EVALUATION September 25, 2014


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While the total number of citations issued during the high visibility enforcement period remained
similar to previous years, the combined use of warnings and citations during the TACT
intervention period appears to have had a positive impact on driving behavior as demonstrated by
the decrease in negative interactions observed in the post-TACT intervention period. While we
cannot directly associate the issuing of warnings and citations with the decrease in negative
interactions, it is interesting to note that shortly after the TACT-enforcement period there is an
overall decrease in the number of citations issued that overlaps with the decrease in negative
interactions observed at our three locations.
Motor Vehicle Crash Data
Purpose: To assess the impact of the TACT enforcement on the number of crashes between
commercial and passenger drivers.
Data Collection: Data were obtained on motor vehicle traffic crashes involving a commercial
vehicle from the Salt Lake City Police Department Record Management System for the years
2012-2014 to control for any temporal trends that may exist outside of the TACT intervention.
SALT LAKE CITY TACT EVALUATION September 25, 2014


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Key Findings: While it is expected the number of commercial vehicle crashes during the TACT
study period will decrease, it is unlikely that we will be able to demonstrate statistical
significance due to the relative rareness of these events.

Table 3 below shows the counts of commercial vehicle crashes that occurred before, during and
after the TACT intervention window dates in each year. The counts display a considerable
amount of variability and do not clearly indicate an identifiable trend.

Table 3. SLC TACT Crashes Involving a Commercial Vehicle by Enforcement Time
Period and Year
Year

2012
(N =12)
2013
(N =34)
2014
(N =20)
Time Period
Pre-Enforcement (J an/1-Mar/14) 4 (33.3%) 30 (88.2%) 13 (65.0%)
Enforcement (Mar/15-Apr/18) 5 (41.7%) 2 (5.9%) 2 (10.0%)
Post-Enforcement (Apr/19-J un/30) 3 (25.0%) 2 (5.9%) 5 (25.0%)
Crashes exclude Public Transit, School Buses and single vehicle collisions.
Year= January through June of each year


Table 4 displays a summary of the characteristics of drivers involved in commercial vehicle
crashes. Except for commercial drivers in 2012, the three years showed similar results in driver
gender. Driver age was similar in all three years. Notably, the proportion of passenger and
commercial drivers that contributed to the crashes is also roughly equal for all three years.
Additionally, most crashes resulted in no or minor injuries.

SALT LAKE CITY TACT EVALUATION September 25, 2014


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Table 4. SLC TACT Crash Driver Characteristic Summary by Year
Year
2012 2013 2014
Passenger Commercial Passenger Commercial Passenger Commercial
N 13 13 33 36 20 18
Sex
Female 3 (23.1%) 9 (69.2%) 8 (24.2%) 0 (0.0%) 8 (40.0%) 0 (0.0%)
Male 10 (76.9%) 4 (30.8%) 25 (75.8%) 36 (100.0%) 12 (60.0%) 18 (100.0%)
Age
Min, Max 23, 61 22, 73 19, 89 23, 66 20, 74 22, 71
Median [Q1, Q3] 41 [35, 50] 33 [23, 38] 43 [31, 59] 43 [34, 51] 42 [32, 58] 42 [30, 48]
Driver
Contributed

Contributed to
Crash
5 (38.5%) 7 (53.8%) 18 (54.5%) 18 (50.0%) 12 (60.0%) 10 (55.6%)
Injury Type
No Injury 11 (84.6%) 5 (38.5%) 25 (75.8%) 32 (88.9%) 19 (95.0%) 15 (83.3%)
Possible Injury 2 (15.4%) 2 (15.4%) 2 (6.1%) 1 (2.8%) 1 (5.0%) 2 (11.1%)
Non-
Incapacitating
Injury
0 (0.0%) 5 (38.5%) 4 (12.1%) 0 (0.0%) 0 (0.0%) 1 (5.6%)
Incapacitating
Injury
0 (0.0%) 1 (7.7%) 1 (3.0%) 1 (2.8%) 0 (0.0%) 0 (0.0%)
Unknown 0 (0.0%) 0 (0.0%) 1 (3.0%) 2 (5.6%) 0 (0.0%) 0 (0.0%)
Crashes exclude Public Transit, School Buses and single vehicle collisions.

As expected no statistically significant associations could be identified from the crash data due to
the relatively rare occurrences of commercial vehicle crashes. In 2014, there were only two
commercial vehicle crashes during the high visibility enforcement period, matching the number
observed in the year before but less than half of the number from 2012. Our data show that a
crash between commercial and passenger vehicle drivers continues to primarily involve males
SALT LAKE CITY TACT EVALUATION September 25, 2014


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between the ages of 30 and 50 years suggesting that future high visibility enforcement and media
campaigns be targeted at this demographic.
Conclusions
Our data demonstrates that there was a decrease in negative interactions in the targeted behavior
areas following the TACT intervention. Specifically, we found a significant decrease in the
overall number of negative interactions at each of our three observation locations, with the
greatest decrease being observed in Following Too Close. Salt Lake City police officers issued
between 40 and 50 citations and warnings each day during the high visibility enforcement
period. The increase in citations towards the end of the high visibility enforcement period may
have contributed to the observed decrease in negative interactions and citations issued during the
post-TACT period. While there were not enough crashes to detect any statistical trends that may
exist in the data, we did find that males between the ages of 30 and 50 years continue to make up
the majority of drivers involved in commercial and passenger vehicle crashes. Future efforts
targeting this demographic are likely to have the greatest impact on reducing crashes.
SALT LAKE CITY TACT EVALUATION September 25, 2014


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APPENDIX 1. OBSERVATIONAL PROTOCOL
Introduction
The goal of the SLC TACT project is to reduce unsafe behaviors and decrease crashes between
passenger and commercial vehicles. The SLC TACT intervention will consist of concentrated
media and increased enforcement to encourage passenger and commercial vehicle drivers to
travel safely around one another within the city limits. The SLC TACT intervention will focus on
four targeted behaviors for drivers of both passenger and commercial vehicles: 1) failing to yield
the right-of-way, 2) disregarding traffic signals, 3) improper turn, and 4) following too closely.
Media efforts will raise driver awareness by educating passenger and commercial vehicle drivers
about how to safely interact with one another on the roadway and the importance of avoiding the
four targeted behaviors. Police officers will reinforce the media messages and help change driver
behaviors by issuing citations to passenger and commercial vehicle drivers when any of the four
targeted behaviors are observed. In addition, the accuracy and use of citations will increase as
traffic enforcement officers use the NCIC codes when issuing citations.
Study Design
This is an observational study design. Data collection will be conducted by two person
observation teams. All observers will receive both classroom and field training. University of
Utah investigators will make unannounced visits to scheduled data collection locations in order
to ensure data are being collected according to the research protocol.
Sample Design
We have selected observation sites according to data received from SLC PD and UDOT. These
sites were determined to have the highest rate of commercial vehicle travel and therefore provide
the greatest opportunity for passenger and commercial vehicle interactions.
Analyses will be based on the number of commercial vehicles passing the observation location
during the observation period. We expect an average number of at least 40-250 commercial
vehicles per hour to be observed and an average negative interaction rate of two -10 negative
interactions per hour depending on location. Under these assumptions we will have the at least
80% power to detect a 50% drop in negative interactions following the intervention period.
SALT LAKE CITY TACT EVALUATION September 25, 2014


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Data Collection
Site Selection
Intersections were selected according to high frequency of commercial vehicle traffic and
passenger and commercial vehicle crashes. Because some of our targeted interactions are more
likely to occur at an intersection, such as disregarding traffic signals and improper turns, while
others are more likely to occur mid-block, such as following too closely, observations will be
collected from both types of locations.
The sites selected are
• 21S/9W-observations will occur at a large intersection with nearby truck stop
• 21S/7E-observations will occur at an intersection and mid-block locations
• 6N/4W- observations will occur at an intersection and mid-block locations
In the event that an original intersection is permanently or temporarily unavailable, due to road
construction, detours, closure, etc. an alternate site will be selected. Observation teams will be
supplied with specified alternate sites to use if needed.
Training
We will recruit teams of observers to collect data. Observers will be recruited through the
University of Utah with preference given to individuals who have experience in field data
collection. Observers must be able to stand for long periods of time, work outdoors, and
successfully complete the training program. Observer training will be conducted at University of
Utah Department of Pediatrics.
At the conclusion of the classroom training all data collectors will participate in field training
and be required to complete a sample data collection period. The group will review the results of
the sample data collection period to discuss similarities and differences among the individual
results.
Observation Periods and Quality Control
All passenger and commercial vehicle interaction observations will be conducted during
weekdays between 7:00 am and 6:00 pm. The schedule will focus on rush hour (before 9:30 am
SALT LAKE CITY TACT EVALUATION September 25, 2014


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and after 3:30 pm) to increase the amount of commercial vehicle traffic. Data collection will take
place in 45 minute stretches during four hour time blocks.
Observation teams will be supplied with a packet describing the observation location, the
direction to observe, and containing data collection sheets.
Data Collection Forms
Data collection will be accomplished by use of a standardized data collection sheet. Observation
teams will document the location, date, time, location type (intersection or mid-block), and any
alternate site or extenuating circumstances when initiating each survey.
Observation teams will observe as many lanes of traffic as they can comfortably monitor while
observing. When observing at a mid-block location, only one direction of traffic will be
observed. However, when observing at an intersection, two directions will be observed as
detailed in the training. One member of the team will be assigned to count all commercial
vehicles passing the observation site while other team members will identify and record all
negative interactions between commercial and passenger vehicles. Data collection will continue
for 45 minutes at which point the collection team will be allotted a 15-minute break. At the
conclusion of the break, team members will switch roles and begin observing for a new 45
minute period. Four 45-minute observation periods will be expected at each location.
Quality Control Procedures
The University of Utah investigators will make unannounced QC visits to at least one data
collection site per team. During the regular QC visits, we will evaluate the data collection team’s
performance from a distance (if possible), and then work alongside the data collection team. We
will ensure that the data collection team is following the survey protocol including: being on
time at assigned sites, using the appropriate data collection forms, and making accurate
observations of passenger and commercial vehicle interactions.
In the event it is discovered that a data collection team has falsified data, the observation form(s)
will be destroyed and the observation will be duplicated by other trained observers.

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APPENDIX 2. DETAILED INFORMATION ON COMMERCIAL VEHICLE COUNTS BY OBSERVATION
LOCATION

2014 SLC TACT Commercial Vehicle Count Summary Comparison by Location and
Vehicle Type*
Location
2100 S 900 W 2100 S 700 E 600 N 400 W All Locations
I MB I MB I MB I MB Overall
Pre-Enforcement
Truck Count
Number of
Observation
Shifts

16

16

8

8

8

8

32

16

48
Sum 3097 3097 154 93 413 233 3664 326 3990
Mean
(SD)
194
(25.8)
194
(25.8)
19
(9.1)
12
(6.3)
52
(22.7)
29
(8.7)
115
(83.9)
20
(11.7)
83
(81.9)
Post-Enforcement
Truck Count
Number of
Observation
Shifts

21

21

11

7

13

15

45

22

67
Sum 4129 4129 222 76 725 478 5076 554 5630
Mean
(SD)
197
(25.2)
197
(25.2)
20
(9.4)
11
(4.4)
56
(30.2)
32
(12.3)
113
(83.8)
25
(14.4)
84
(80.4)
* I = Intersection; MB = Mid-Block