Having been in this business for nearly twenty years, we have seen roughness issues of all sorts. Roughness can come in the form of sub-grade problems, from pavement age, or from poor quality craftsmanship. There is one kind of roughness, though, that is most easily avoidable: roughness built into the design.

Design roughness most often happens in areas of intersecting runways or when the design is being tied into existing difficult grade changes. The following case explains the consequences of choosing not to perform a roughness analysis on a runway design.

The runway in question is at a major metropolitan airport in the southeast US. This runway was designed, built, and opened before we got the call. When we did get the call, the person explained that one of the first aircraft to operate on the newly opened runway experienced so much response to the roughness that it nearly bottomed out the aircraft’s suspension, causing the pilot to complain. As the days progressed, the airport quickly realized they had a problem, as several pilots had made their complaints known to the tower. The airport wanted APR to solve two problems: What went wrong? Who was at fault?

After making profile measurements using our Auto Rod and Level, we went to work determining the exact location and severity of the roughness. Once we determined that, we entered the runway’s design into our evaluation software, APRas, and began comparing the as-built pavement with the design.

In the end, we determined that while the contractor did not meet the design perfectly, the design itself was flawed. Even in a perfect construction situation, the pavement would likely still have generated pilot complaints.

Had the design been sent to us before beginning construction, the entire situation may have been avoided. We would have been able to work with the designer to achieve an acceptable design while maintaining non-smoothness related concerns.

We were, however, still able to offer significant cost-savings by determining the exact location of roughness. Instead of re-constructing the entire area, we were able to help them use a combination of panel removal and diamond grinding to alleviate the long-wavelength roughness. In addition, our conclusions helped the pavement owner, contractor, and designer come to an agreement and share the cost of the repairs. This saved potentially millions of dollars in litigation.

The bottom line is that it is much easier and more cost effective to make changes to a design in the office than to change an as-built pavement in the field. Pavement owners and designer must take every precaution to ensure that the design is acceptable before a project goes out to bid. Having your design assessed by APR can be considered as cheap insurance, ensuring that the intended profile produces the ride quality owners and operators want.

Next: a case study of an airport that chose to evaluate an intersection design before construction.