Tuesday, September 27, 2022

What goes into understanding traffic in Wilmington?

Traffic studies are often required for new developments. Those studies give roads a letter grade ranging from A-F (Port City Daily photo/BEN SCHACHTMAN)

WILMINGTON — Sitting in traffic is not something most people would say they enjoy, but it is an unfortunate reality for urban areas and Wilmington is no different.

But where is traffic the worst, where do roads need to be improved  — and how do officials know what the impact of new development will be?

The Port City continues to attract visitors and new residents; estimates have the city seeing a growth of 50,000 new residents in the next few years. So, when it comes to infrastructure improvement in the region, the burden falls on several entities, from the NCDOT to private developers.

With new numerous new developments in Wilmington and New Hanover County receiving approval, more and more developers are being required to conduct traffic impact analyses (TIAs). These studies analyze the amount of traffic on a roadway at specific locations, and then predict the impact new developments will have at these locations.

“The county requires TIAs to be completed for developments that will generate more than 100 trips in either the A.M. or P.M. peak hours,” current planner for New Hanover County Brad Schuler said.

The NCDOT has produced a list of standards that ensure consistent traffic analyses that traffic engineering companies must follow. But even then, traffic impact analyses don’t always show the bigger picture. For example, when the Carroll Companies released its TIA for the proposed development known as The Avenue, the results presented a different narrative than the city’s findings.

While a city report might look at the bigger picture of a roadway’s traffic, a TIA preformed on behalf of a development might only provide information for a few specific intersections.

TIAs will often use a grading system known as a level of service which provides a letter grade ranging from A-F.

According to a city report, the level of service for Military Cutoff Road in a specific location is currently operating at an F level of service (Port City Daily photo/COURTESY CITY OF WILMINGTON)

“When one refers to level of service, it is often in relation to roadway capacities. A Traffic Impact Study is generally performed to determine a level of service,” Brian Rick, communications officer for NCDOT said. “During project development by public or private entities, the traffic analysis is performed to determine pre/post level of service on the roadways affected. The level of service is used to determine potential roadway improvements as not to degraded capacities by the development.”

According to the NCDOT, “The relationship of travel demand compared to the roadway capacity determines the level of service (LOS) of a roadway. Six levels of service identify the range of possible conditions. Designations range from LOS A, which represents the best operating conditions, to LOS F, which represents the worst operating conditions.”

The different levels of services are defined as follows:

  • LOS A: Describes primarily free flow conditions. The motorist experiences a high level of physical and psychological comfort. The effects of minor incidents or breakdown are easily absorbed. Even at the maximum density, the average spacing between vehicles is about 528 ft, or 26 car lengths.
  • LOS B: Represents reasonably free flow conditions. The ability to maneuver within the traffic stream is only slightly restricted. The lowest average spacing between vehicles is about 330 ft, or 18 car lengths.
  • LOS C: Provides for stable operations, but flows approach the range in which small increases will cause substantial deterioration in service. Freedom to maneuver is noticeably restricted. Minor incidents may still be absorbed, but the local decline in service will be great. Queues may be expected to form behind any significant blockage. Minimum average spacing is in the range of 220 feet, or 11 car lengths.
  • LOS D: Borders on unstable flow. Density begins to deteriorate somewhat more quickly with increasing flow. Small increases in flow can cause substantial deterioration in service. Freedom to maneuver is severely limited, and the driver experiences drastically reduced comfort levels. Minor incidents can be expected to create substantial queuing. At the limit, vehicles are spaced at about 165 feet, or 9 car lengths.
  • LOS E: Describes operation at capacity. Operations at this level are extremely unstable, because there are virtually no usable gaps in the traffic stream. Any disruption to the traffic stream, such as a vehicle entering from a ramp, or changing lanes, requires the following vehicles to give way to admit the vehicle. This can establish a disruption wave that propagates through the upstream traffic flow. At capacity, the traffic stream has no ability to dissipate any disruption. Any incident can be expected to produce a serious breakdown with extensive queuing. Vehicles are spaced at approximately six car lengths, leaving little room to maneuver.
  • LOS F: Describes forced or breakdown flow. Such conditions generally exist within queues forming behind breakdown points.

What about NCDOT infrastructure improvements?

While developers and local governments do perform infrastructure upgrades, the North Carolina Department of Transportation is responsible for many large-scale improvements throughout the state. In August, the North Carolina Board of Transportation approved the 10-year plan known as the 2018-2027 State Transportation Improvement Program.

“The STIP is a multi-year capital improvement document which denotes the scheduling and funding of Highway and Non-Highway projects across the state, over a minimum four-year time period as required by state and federal laws. North Carolina’s STIP covers a 10-year period …The STIP was developed under the Strategic Transportation Investments (STI) law passed in June 2013. The law elevates the use of transportation criteria and input of local communities to determine project priorities and directs the use of dollars from the state’s Highway Trust Fund for construction,” Rick said.

The STIP has identified more than 750 highway projects across the state and a total of 1,367 projects that include aviation, rail, ferry, public transit, and more – several of which are in New Hanover County. NCDOT also provides an interactive map that provides project information across the state.

As the Cape Fear region continues to grow, the STIP as well as TIA studies will continue to be referenced during local government meetings.


Michael Praats can be reached via email at Michael.p@localvoicemedia.com.

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