Across the United States, state DOTs, engineers, and other contractors are busy working on highway bridges. This work entails routine maintenance, repairs, and even rehabilitation in many cases. 

And then there are the highway bridge inspections.

With more than 620,000 highway bridges scattered across the landscape in all 50 states, the sheer volume of work bridge inspections requires is mind-boggling. And that’s just including the routine inspections. 

Given that most bridges are being inspected every two years at a minimum – and some even more often – this accounts for upwards of 300,000 inspections every year. This can average over 1,000 bridge inspections taking place each weekday.

And there are more than “routine” inspections taking place.

A Brief Look at the Standard Categories of Highway Bridge Inspections

The most common bridge inspections carried out are what the Federal Highway Administration (FHWA) refers to as Routine. However, there are five basic types of inspections, according to the U.S. Department of Transportation (USDOT):

In fact, the federal government defines five basic categories of bridge inspection types:

  • Initial
  • Routine
  • In-depth
  • Damage
  • Special

The first official bridge inspection carried on a new or rebuilt structure is the “initial” inspection.

This first inspection serves to provide critical information such as the structure inventory and all the appraisal data. In addition, the initial inspection serves to establish the baseline structural conditions, as well as identify and document any existing structural issues or any locations in the structure that may present potential problems.

The most common type of inspection, the “routine” inspection, is generally required to be carried out every two years. The primary purpose of these bi-annual inspections is to determine the physical and functional condition of highway bridges on a regularly scheduled basis.

There are certain situations when an “in-depth” inspection is deemed necessary. This is a close-up, hands-on inspection of one or more members that can be located either above or below the water level and is conducted to identify potential deficiencies that are not easily detectable during typical routine inspections.

A more obvious need is what is termed as a “damage” inspection. These are emergency inspections conducted to assess any structural damage immediately following an accident or as the result of unanticipated environmental factors or human actions. These could include extreme and exceptional flooding, for example, or overt efforts to damage a bridge structure.

Lastly, the category of “special” inspections serve to regularly monitor any known or suspected deficiencies identified in a highway bridge structure.

Common Types of Highway Bridge Inspections

Generally speaking, the types of inspections carried out for any of these several categories of highway bridge inspections can vary depending on the need and the issues being addressed by the inspectors.

These inspection methods include the following:

  • Periodic Inspections

These standard inspection types are also known as routine inspections. Typically, they are carried out in accordance with the federally mandated highway bridge inspection schedule. Inspectors focus on the general condition of the bridge, largely relying on visual inspection, and document visible changes from the previous scheduled inspection. The primary purpose is to ensure the bridge continues to be safe to operate according to existing standards.

  • Underwater Inspections

Many highway bridges span waterways and any underwater infrastructure that supports a bridge must be inspected by specially trained personnel often using diving equipment. During these types of inspections, the entire submerged exterior of bridge piers and abutments are inspected for signs of erosion, physical deterioration, visual signs of distress, and to assess the extent of water scour.

  • Damage Inspections

As noted above, these unscheduled bridge inspections are required If structural damage is either known or suspected. In those situations, bridge engineers will call for an urgent damage inspection to assess the extent of the damage, its cause, and possible repairs.

  • Fracture-Critical Member Inspections

According to an article in, “A fracture critical bridge inspection is defined by the NBIS as a “hands-on” (i.e. within arm’s length of the component) inspection of fracture critical members. This type of inspection uses visual methods that may be supplemented by non-destructive testing (NDT).”

Common Techniques Employed for Highway Bridge Inspections

There are a variety of tools and techniques used during various types of bridge inspections. The more common ones include:

  • Visual inspections that require bridge inspectors to visually assess the visible condition of the bridge in detail, both on and above the bridge deck as well as underneath. 
  • Acoustic inspections utilize tools such as hammers, chain drags, or other specialized instruments that allow inspectors to observe changes in sound pitch on the bridge deck.
  • Thermal inspections employ highly specialized instruments that collect thermal or infrared data that can detect changes in infrared radiation from the surface of a bridge, which can be an indication of concrete degradation or delamination.
  • Ground-penetrating radar (GPR) uses electromagnetic radiation that inspectors use to create images of regions beneath the concrete in a bridge. The results can reveal minor defects such as cracks or delamination in the bridge structure materials.

Under Bridge Platforms is Your Partner for the Best Under Bridge Inspection Equipment

No matter what type of highway bridge inspection you need to carry out, having the best choice for your under bridge access needs is critical to safely completing your project.

Under Bridge Platforms serves all of the Western States, including California, Washington, Oregon, Idaho, Nevada, Montana, and Wyoming to provide quality under bridge equipment.

Our large and expanding inventory of under bridge access platforms includes state-of-the-art bridge access platforms such as the versatile Aspen Aerials A-30 bridge inspection platform as well as the far-reaching HPT 43 Truck Mounted Platform.

In addition, we carry a wide variety of bridge inspection platform vehicles that all feature multiple capabilities. Along with reach and platform size, determining the best choice for your bridge inspection, maintenance, or repair work also depends on both the bridge structure and the terrain underneath. 

We are also proud to be the only company in our industry based in California that offers total under bridge access. And by consistently providing high quality customer service, we have managed to build long-lasting relationships with our esteemed customers.

All of which are qualities that we work hard to keep that way. 

So, contact us today and let us help you with your under bridge platform and bridge access needs.