Appreciation of the traffic effects on the RST by infrared thermography

Abstract

Road surface temperature forecast is a key component of winter maintenance strategy in many developed countries. Numerical tools exist to help road managers to organize services and consequently to trigger de-icing operations. Forecasting strategies have been commonplace since the 1980s, and often based on numerical models. Traffic is one of the influencing parameters, specifically in urban areas. This work was undertaken to evaluate to which extent an accurate description of traffic might improve numerical model dedicated to road surface temperature forecasting. Two sets of experiments were run to detect and to quantify traffic effects on RST. First one consisted in driving above an infrared radiometer, a pyrgeometer and other atmospheric probes to measure the radiative contribution of a passing vehicle at various speeds. In the second set, an infrared camera was installed on a vehicle in an urban traffic flow. This camera was mounted on the roof and focused the pavement right behind the vehicle ahead, both circulating at the same speed. Infrared thermography indicated a fleeting contribution of traffic to RST. The temperature increase in circulated areas, with respect to uncirculated ones, does not last according to collected measurements. Measurements with atmospheric and radiometric probes provided elements to properly take into account traffic in a numerical model and to appreciate its contribution.

Accounting for anthropic energy flux of traffic in winter urban road surface temperature simulations with the TEB model

“…Furthermore, Fujimoto et al (2010) reported that the RST under vehicles waiting at traffic signals was 3 to 4°C higher than that nearby. Some experiments with a thermal mapping vehicle indicated that traffic has a significant effect on RST (Khalifa et al, 2014), especially in traffic light areas and/or on roads with high traffic density.…”

“…The radiative fluxes emitted by the upper and lower parts of vehicles were also specifically considered by Ishikawa et al (1999) and Takahashi et al (2005), and were based on the Stefan-Boltzmann law. A presentation of modified equations to take into account these processes in the TEB model was made and fully described in a previous paper (Khalifa et al, 2014), and illustrated in Fig. 4a.…”

“…Furthermore, shielding due to vehicles on the road and the impact zone of their associated physical processes is partial. Khalifa et al (2014) have identified an impact factor for each traffic physical process to evaluate its contribution, as indicated in Fig. 4b and Tables 1 and 2. In the following paragraphs, we have attempted to summarize the different approaches found in the literature and that have been analyzed in order to identify and to evaluate the different thermal traffic processes.…”

“…This physical traffic process can be evaluated by a shield effect coefficient C shield (dimensionless number). The vehicle shield effect on the road has been investigated by Khalifa et al (2014) and can be defined by the following expression:…”

Thermographic monitoring of asphalt concrete surface with phase change materials inclusions for icing delays purposes

“…Despites years of efforts in terms of staff training, evaluations on economical costs [1] of winter maintenance, on its environmental impacts, the improvements in weather forecast through numerical models [2][3][4][5], hundreds of tons of de-icers are still spread over pavements surfaces. One last mean to influence this de-icer trend is to implement a change in the infrastructure itself to avoid black ice occurrence and snow accumulation over the surface submitted to traffic.…”