Air Flow Testing for Highway Tunnels

By Kelly Hile

U.S. road tunnels are used by over 15 million motorists every day


As a fluid dynamics solutions company, Airflow Sciences has decades of experience with fan performance testing and ventilation system design. Our engineers evaluate HVAC systems, perform numeric modeling of air flow in buildings, and analyze fan performance. Proper ventilation is an important factor in many different industries, and one area of testing we conduct is in the transportation industry, where we test air flow in tunnels.

Why Highway Tunnels Need Air Flow Testing

Highway tunnels play a vital role in the transportation infrastructure of the United States. Not only do tunnels create safer, more efficient travel routes for commuters, but they also support the movement of goods and services nationwide. The Federal Highway Administration reports that over 500 roadway tunnels are in operation today, covering over 130 miles and carrying over 15 million vehicles every day. These routes often facilitate travel in otherwise difficult geographies, helping key travel continue in spite of mountain terrain and waterways.

Tunnels on roadways need to have sufficient air flow to prevent buildup of exhaust emissions. In many cases, tunnels are equipped with sensors that detect carbon monoxide and make automatic adjustments to dissipate harmful vapors. Ventilation systems can consist of a few simple fans, or they can include entire air supply and return systems that run above or beneath the tunnel. Inadequate ventilation can have some serious consequences, especially when it comes to risk events like vehicle fires, when smoke and heat must be cleared quickly. In emergency situations, proper airflow can make the difference between life or death for trapped travelers.

Federal Regulations Require Inspection of Tunnels

flow rate of a fan in a tunnel being tested
fan flow rate test in progress
Vane anemometers being used to test the flow rate of a fan in a tunnel


The Federal Highway Administration requires regular inspection of tunnels throughout the United States. Similar to the National Bridge Inspection Standards, the National Tunnel Inspection Standards ensure that tunnels are checked for structural and operational health, including ventilation systems. When we evaluate these systems, we assess the flow rate and static pressure rise generated by fans at various operational settings. We can also assess the entire ventilation system, including supply and return plenums. We assess any ventilation system, whether longitudinal, traverse, or semi-traverse, and we test any type of fan, whether centrifugal, propeller, or axial.

Our Highway Tunnel Testing Services

highway tunnel testing in progress

ASC testing crew conducting fan performance testing on a new fan installed for ventilation in a traffic tunnel. The testing was conducted using hot wire velocity probes and our custom test hardware.

As a flow testing service provider, we offer state-of-the-art equipment accompanied by the highest level of industry experience. We determine the most ideal test set-up, furnish all measurement devices, and most importantly, we provide tunnel owners and transportation departments with the accurate flow data they need to keep their roadway assets protected and maintained.

Contact us today to learn more about our highway tunnel testing services.

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