Exterior Roadside Noise Associated with Centerline Rumble Strips as a Function of Depth and Pavement Surface Type

Controlled field studies were performed at 12 locations to evaluate the impacts of milled centerline rumble strips on exterior roadside noise adjacent to rural two-lane highways as a function of rumble strip depth and pavement type. Twenty controlled pass-bys were performed at each location using a minivan traveling at $88.5\mathrm{km}/\mathrm{h}$ (55 mph). An equal number of passes were made both while traveling on and off of the centerline rumble strips, with the latter condition providing baseline noise data. The maximum noise was recorded during each pass using a digital sound meter that was placed 15.24 m (50 ft) laterally from the centerline of the roadway at a height of 1.52 m (5 ft) above the pavement surface. Multiple linear regression models were estimated to ascertain the effects of depth and pavement type while controlling for baseline noise. The milled depth of the rumble strips was the strongest predictor of roadside noise, and this effect was stronger for hot mix asphalt pavements compared to chipsealed pavements. For every 1.5875 mm ($1/16\text{-}\mathrm{in.}$) increase in centerline rumble strip depth, roadside noise increased by 2.3 decibels on hot mix asphalt pavements, compared to 1.4 decibels on chipsealed pavements.