Traffic Studies - Yarger Engineering, Inc. 317-475-1100 Email Us
What is a Traffic Study, Traffic Impact Study (TIS), Traffic Impact Analysis (TIA), or Traffic Operational Analysis (TOA)?
The first thing to know is that a Traffic Impact Study (TIS) and a Traffic Impact Analysis (TIA) are basically the same thing with slightly different names. A Traffic Operational Analysis (TOA) is basically a simplified traffic impact study. They are all traffic studies, but there are other types of traffic studies that are usually done for a governmental agency for their needs. Traffic impact studies are prepared by consulting traffic engineers for developers or others wanting to build new or expand real estate developments, such as shopping centers, office parks, industrial plants, schools, hospitals, or other such developments. Smaller developments such as gas stations may not warrant a full TIS, but may warrant a TOA. The purpose of the traffic impact study is to identify traffic impacts of the proposed development, hence the name. The impacts are primarily congestion or safety related. INDOT has their own traffic impact study guidelines, as do most larger communities. They are usually based on the recommended practice of the Institute of Transportation Engineers. A traffic impact study report is the written document that contains the information from the study. It usually will have an appendix that contains the raw data and calculations. The following will refer to traffic impact studies, but apply to traffic impact analyses. traffic impact assessments, and traffic operational analyses.
The items that typically go into a traffic impact study are:
- Proposed development land uses, sizes and phasing
- Study locations, primarily intersections
- Existing traffic, usually turning movement counts including cars, trucks, pedestrians and bikes, and hose counts
- Times of days, days of week, and horizon years (future years to be studied)
- Expected traffic growth without development
- Expected nearby (off-site) developments
- Crash history
The items that are output are:
- Existing congestion, typically in terms of level of service (A-F like in school), delay and queue lengths
- Existing queue lengths (number of stopped vehicles in lane, typically measured in feet)
- Forecasted traffic
- Forecasted congestion and queue lengths
- Alternatives for addressing the congestion and crash problems, such as:
- Additional lanes
- Signs
- Markings
- Signals
- Roundabouts
- Sidewalks
- Bike paths
- Sight distance improvements
- Lighting
What does a traffic study cost?
The typical answer is “about the same as a car…” Of course, not everyone needs the same car. Some can use a 15 year old Chevy while others want a brand new Ferrari, and occasionally someone will need a dump truck. Referring to the inputs above, the main cost driver is the number of intersections. Other items that also drive the cost are the location, times of days, days of week, years, development scenarios and the number of land uses. A general rule of thumb is $3,500 per intersection, but that can range from $2,500 to $5,000 for three or more intersections, or in one case, $13,000 for a single intersection with a large multi-phased development. Traffic operational analyses as mentioned above are simplified traffic impact studies. Normally they are limited to only one horizon year of when the development opens and few if any off-site developments. They may also not address as many issues as a full traffic impact study. They typically run $2,000 to $3,000 per intersection.
How long does a traffic study take?
Like the cost, it is a function of the inputs, but typically one week per intersection for straight forward studies. Traffic data collection can impact the duration of a study. On one study, we had to wait a couple of months for nearby road construction to be completed, and then a couple more weeks for the local schools to return from a fall break. Of course, weather and holidays can also delay collecting traffic counts.
Next step
Once the traffic study is complete, the next step is to turn the study recommendations into construction plans and get permits. Yarger Engineering, Inc. prepares road, signal, signage and marking plans for submittal to governmental agencies for permits.
Yarger Engineering offers free initial consultations and proposals, and we would be glad to discuss your situation. Call us at 317-475-1100 or email us about your study today!