How Warehouse Growth & Modern Truck Traffic Are Overwhelming Lehigh Valley Roads

Certain intersections present elevated crash risk today because their geometry no longer matches the turning characteristics of the vehicles that routinely use them.

In transportation engineering, this condition is known as a design-vehicle mismatch. Intersection curb radii, lane widths, and channelization were often developed for smaller vehicles and do not adequately accommodate the way modern 53-foot semitrailers execute turns.

These intersections were not improperly designed when constructed. Rather, the demands placed on them have changed. Warehouse growth and increased tractor-trailer volumes have altered traffic composition beyond what the original designs anticipated.

At low speeds, a trailer’s rear wheels cut inside the path of the cab’s front wheels. The Federal Highway Administration refers to this as low-speed off-tracking.

Because of this, a truck must swing wide before turning to avoid striking the curb or roadside objects. That wider approach often requires the truck to occupy adjacent lanes.

Under typical conditions, a standard semitrailer executing a right turn can require space equivalent to nearly two full traffic lanes. This is not aggressive or careless driving. It is a physical requirement dictated by vehicle geometry.

Even when a driver is careful and moving slowly, the trailer will naturally track inward. To compensate, the cab must move outward. The result is a turning movement that appears unusual but is entirely necessary.

This is where many crashes occur, not because of erratic driving, but because of misinterpretation.

Drivers rely on prior experience with passenger vehicles when interpreting movement. When a tractor-trailer initiates a wide turn, it can appear to create an open lane beside it. At that moment, some motorists make a gap acceptance decision, concluding incorrectly that there is enough space to pass.

In reality, that space is part of the truck’s turning path. As the trailer tracks inward, the vehicle moves directly into the space the driver thought was open.

The conflict is not random.  It is the predictable result of geometry and human perception.

Even when intersections are redesigned to better accommodate trucks, perception-based errors can still occur. The visual cue of a wide swing continues to invite misjudgment, regardless of whether the geometry technically meets modern standards.

Skewed Intersections

A skewed intersection is one where roads meet at angles other than 90 degrees, often 60 to 75 degrees.

These intersections change geometry, timing, and visibility all at once. Compared to standard right-angle intersections, skewed intersections:

• Increase crossing distances
• Keep vehicles in the intersection longer
• Cause turning movements to overlap more

For trucks, this means:

• More time blocking lanes during turns
• Greater likelihood of vehicles entering conflict zones mid-maneuver

As warehouse traffic increases, these weaknesses are exposed more frequently. Skewed intersections become recurring conflict points, especially on roads built before modern freight volumes existed.

Tight Curb Radii and Limited Turning Infrastructure

Airport Road (Hanover Township Corridor)

Airport Road has seen a sharp increase in truck traffic, with thousands of heavy trucks traveling the corridor daily. It now functions as a freight access spine rather than a typical local road.

Frequent turning movements at intersections with limited geometric capacity create conditions where adjacent lanes are not reliably available during truck turns. In some cases, infrastructure conflicts, such as contact with overhead signal equipment, have required corrective planning measures.

PA 329 (Nor-Bath Boulevard) & Weaversville / Howertown Road

Planning documents identify this area as having challenging geometry for trucks. Existing layouts require trucks to operate within space that was not designed for frequent tractor-trailer movements.

As a result, trucks often need to set up wide for turns, temporarily using more than one lane to complete maneuvers safely.

Route 100 & Tilghman Street

This intersection sits within one of the region’s most intense warehouse growth corridors. Truck turning volumes have increased significantly as industrial development has expanded.

However, the underlying road design reflects older assumptions about traffic composition. This mismatch leads to repeated encroachment into adjacent lanes and increases the risk of conflict during turning movements.

Union Boulevard / Irving Street / Airport Road (Allentown)

This five-legged, skewed intersection has been identified as a high-injury location. It carries substantial daily traffic and has experienced multiple serious and fatal crashes.

Its irregular geometry creates overlapping movements and visibility challenges. Combined with mixed commercial, residential, and transit activity, the intersection presents numerous conflict points for both drivers and pedestrians.

Drivers can reduce risk by understanding how trucks move and recognizing early warning signs.

Watch the truck’s front wheels

If the front wheels are angled outward or positioned away from the curb, the truck is preparing for a wide turn.

Notice how far forward the truck stops

Drivers often pull forward to straighten the trailer before turning. This indicates the turn will not stay within one lane.

Look at the curb

Tight, sharp corners signal that a truck will need additional space to turn.

If the truck pauses mid-turn, it’s protecting space

A slow or paused turn is usually a sign the driver is managing the trailer’s path, not yielding.

Respect the gap

Never attempt to pass a turning truck on the inside. The space beside the truck is part of the path the trailer must occupy.

Defensive positioning

Stay out of blind spots and leave space near intersections where trucks are turning.

For drivers who have already been involved in a crash with a tractor-trailer, understanding how these incidents happen is often critical when evaluating potential legal claims.

• Painted lane lines (they do not change truck physics)
• Turn signals alone
• The assumption that the trailer will stay within its lane