July 26, 2016

Research in Our Ranks: Porous Pavement Bike Lanes

Photo of bike tire

Transportation has always been one of Davis & Floyd’s strongest sectors and because of that we recognize that the challenges of public transportation are often about integrating options beyond automotive.

That is why we wanted to take a minute to highlight research done by one of our own – Tripp West, PE. An engineer in the Charleston office, Tripp works on project teams for water resources, transportation, and land development projects for both public and private clients. Through design, preparation of plans and specifications, permitting, and cost estimating, he has been essential on multiple plans, analyses, and developments.

Tripp always has been passionate about helping others meet their basic needs, from clean water to safe living spaces, access to work, and a means to move people and goods. While working on his engineering degree, he was a founding member of a group called Clemson Engineers for Developing Countries. His focus on sustainability is one reason he believes that engineers can make great strides as we tackle future problems like climate change and rising sea levels.

With that in mind, we wanted to share some of Tripp’s thesis research on porous pavement bike lanes adjacent to impervious traffic lanes. He was able to analyze the distance required for water running onto a porous pavement to fully infiltrate into the pavement – proving that it is linearly proportional to the width of the adjacent impervious traffic lanes and the rainfall intensity. It is also inversely proportional to the sum of the rainfall intensity and pavement hydraulic conductivity.

Why are his findings on porous pavements so important? We will let Tripp explain:

The inclusion of bicycle lanes or pathways is increasing in urban areas where local governments are looking for ways to increase alternative modes of transportation and provide safe routes for the increasing number of cyclists choosing to ride their bicycles around town rather than drive a vehicle. Even from a site design perspective, we are now required to include in our plans how pedestrian and bicycle access will be accommodated within our developments and how those pathways will connect to existing routes. One of the leading causes of increased flooding is the conversion of pervious areas (forests, farmland, and other open spaces) to impervious areas (buildings and pavement), which increases the volume of downstream runoff leading to potential flooding issues. The addition of paved bicycle lanes and pathways in a road corridor further increases the total amount of impervious area required for that facility.

Pervious pavements, which allow water to drain through the surface, are already being used in other applications where traditional pavement is required to reduce the overall volume of runoff leaving a site. The goal of this project was to investigate the feasibility of using pervious pavements for the bicycle lane application and then identify which components of the system would need to be further investigated in hopes of creating a design guideline for using this application in practice.

The pervious bicycle lane concept could potentially be implemented within new road corridors, alongside existing roadways, or incorporated into maintenance and retrofits of existing streets.

Today, Tripp and his Davis & Floyd colleague Mike Horton are serving in an industry advisor role with his former professor on a new research project. The project, entitled “Performance Based Design of Low Impact Development Technologies in Response to Climate Change Induced Changes In Rainfall Patterns,” is funded through the SC Sea Grant Consortium.