Evaluation of Urban Heat Island Effect on Road Pavement Temperature in Lagos Metropolis

Urban heat island effects in Lagos metropolis, South West Nigeria, elevate ambient and pavement surface temperatures beyond design assumptions, potentially contributing to premature asphalt deformation, rutting, and surface cracking in flexible road pavements. This study evaluates the influence of the urban heat island effect on road pavement temperatures in Lagos metropolis. Pavement surface temperatures were measured at six locations representing different urban intensity categories (urban core, suburban, and peri-urban) using a calibrated infrared thermometer at three times of day: morning, afternoon, and evening, over eight consecutive weeks during the dry season. Concurrent air temperature readings and urban cover density maps were compiled. Asphalt specimens from each pavement type were tested for dynamic creep and wheel-tracking performance at measured peak temperatures. Results indicate that pavement surface temperatures in the urban core reach a peak mean of 64.2 degrees Celsius, compared to 52.8 degrees Celsius in peri-urban locations. Peak temperatures in the urban core exceed the critical temperature for asphalt rutting initiation in 78 percent of afternoon measurements. Wheel-tracking tests confirm permanent deformation rates three times higher at urban core temperatures than at peri-urban temperatures for equivalent binder grades. The study recommends the use of high-performance polymer-modified binders and light-coloured aggregate chippings on heavily trafficked urban roads in Lagos to mitigate thermal pavement distress.

Keywords: urban heat island, pavement temperature, asphalt rutting, Lagos metropolis, South West Nigeria