Traffic Congestion

The Roanoke Valley does not have much severe traffic congestion – and we want to keep it that way. Residents view short travel times as a quality of life benefit. However, economic development and tourism efforts to attract people and businesses can increase traffic and threaten the short travel times. The Congestion Management Process describes strategies to manage traffic even as the population and economy grow in the Roanoke Valley.

Everyone knows what congestion is – it’s what they experience when they’re trying to get somewhere. Measuring congestion objectively is challenging. With the advent of GPS-equipped vehicles and smart phones, big data provides a real picture of traffic congestion and has led to the creation of several congestion indices. The Planning Time Index is appropriate for the Roanoke Valley, a region without much severe traffic congestion, because it is relevant to incident management.

Planning Time Index is the trip time of 95% of the trips on a segment divided by the amount of time it would take to travel the segment in free-flow conditions. For example, a Planning Time Index of 2 means a 10-minute trip takes more than 20 minutes 5% or more of the time. Other regions that use Planning Time Index set the threshold at PTI 2.5 for off-peak and PTI 3 for peak hours. The RVTPO is using these thresholds and defines peak hours as 7-9 am and 4-6 pm.

Here’s the entire region over seven years, followed by individual routes shown separately. This map confirms that the Roanoke Valley does not have much severe traffic congestion, but has brief hot spots.

I-18 has a terrible reputation, but by the objective Planning Time Index, it is surprisingly reliable.

How about US 460?

I-581 and US220 (south)

US220 and Route 419

Route 419 (Electric Rd)

Alternate 220 (Cloverdale Rd)