Brett W' Blackadar, P'E'

1
Using Travel Time and Delay Data To
Determine Capacity Improvement Needs
SEMINOLE COUNTY ENGINEERING
Presented by
Brett W. Blackadar, P.E.
2
Words of Wisdom

• We think too small. Like the frog at the bottom
  of the well. He thinks that the skyis only as
  big as the top of the well. If he surfaced, he
  would have an entirely different view.

- Mao Tse-tung
3
www.seminolecountyfl.gov/pw/eng/timestudy.asp
4
(No Transcript)
5
Source Highway Capacity Manual 2000
6
Source Highway Capacity Manual 2000
7
Interesting Fact
Most of us have eaten a spider in our sleep.
8
Benefits of Travel Time and Delay Studies

• It provides real-time data on the operations of
  roadways.
• It can be used to determine capacity
  deficiencies which can be translated into future
  capital improvement projects.
• If data is collected yearly, historical data can
  be assembled which can help determine
  deteriorating capacity trends and therefore
  potential future projects.
• It can be used to compare before and after
  conditions for completed capacity improvement
  projects.
• It provides data to calibrate traffic studies
  done within the County.
• It can assist the Traffic Concurrency approval
  process.

9
Words of Wisdom
Significant problems we face cannot be solved at
the same level of thinking we were at when we
created them.
Albert Einstein
10
Statement from FDOT 2002 Quality / LOS Manual
FDOT does not recommend the use of travel time
studies for LOS planning applications. Travel
time studies have the advantage of being real
world data however, their use in assigning LOS
for a facility is limited for three major
reasons (1) cost and variability of results, (2)
application to a specific time period, and (3)
use for future year analyses.
11
1. Cost and variability of results

• The FDOT Manual on Uniform Traffic Studies
  (January 2000) provides a study procedure for
  Travel Time and Delay Studies.
• The Manual suggests a permitted error of 3.0
  mph for before and after studies.
• Using the provided formula in the study
  procedure from the manual along with data from
  our 1999 Travel Time and Delay Study, it was
  determined that a minimum of 5 runs per peak
  direction was required.
• We do 6 runs for County roadways and 8 runs for
  State roadways.
• Our cost is about 70,000 for approximately 170
  miles of roadway.

12
2. Application to a specific time period

• FDOT uses the 100th highest hour of the year for
  analysis of the roadway.
• It is difficult to determine the 100th highest
  hour without taking an exorbitant amount of
  travel time and delay data.
• The alternative is to find the closest FDOT
  permanent count station and determine the what
  time periods constitute the peak periods for that
  specific area.
• The travel time and delay data can be
  coordinated to occur during those periods.
• In Seminole County, we collect data from January
  through March while public school is in session.

13
3. Use for Future Year Analysis

• There is no way to project existing year travel
  time and delay data to future design years.
• However, the results of the existing year travel
  time and delay data can be used to calibrate the
  existing year analysis from analysis packages
  such as ArtPlan and simulation packages such as
  CORSIM and Synchro.
• Once the existing year analysis is calibrated,
  the software package can be used for future year
  analysis.

14
Words of Wisdom
The man who makes no mistakes does not usually
make anything.
Edward Phelps
15
Interesting Fact
In the United States, more people are killed
each year by vending machines than shark
attacks.
16
Challenge 1 - Segment LOS vs. Section LOS
17
(No Transcript)
18
Challenge 2 - Segment Length and Signal Delay
19
(No Transcript)
20
Challenge 3 - Data Collection Period vs. Peak
Hour
21

• Based on yearly traffic counts, the AM peak hour
  was determined to be from 715 815 AM
• Data for the AM peak hour Travel Time and Delay
  study was collected between 717 842
• When using Travel Time and Delay data to
  calibrate traffic studies, only look at data
  within the peak hour

22
Conclusions

• Travel Time and Delay Data can provide valuable
  information on the condition of a roadway system
  for a reasonable price.
• It is a snapshot of the existing conditions and
  cannot be directly used to analyze future
  operational conditions.
• However, the data can be used to calibrate the
  existing conditions of models such as CORSIM and
  Synchro and also for the FDOT LOS Software
  ArcPlan.
• The data can be misinterpreted. Make sure to
  analyze the proper roadway segment and the
  appropriate peak period.

23
Interesting Fact
40,000 Americans are injured by toilets each year
24
Questions?
Brett W. Blackadar, P.E. Principal Engineer,
Engineering Division Seminole County Public Works
Department Office 407-665-5702 bblackadar_at_seminole
countyfl.gov