Reducing Icy Conditions Over Bridges, Through Passive

Abstract

Icy road conditions are a major cause for car crashes. 70% of all roads in the United States are 8 located in icy regions, and winter and snow related maintenance account for 20% of the roads 9 maintenance budgets (FHWA, 2017), Snow also reduces the average road speed by 30 to 40% on 10 roads. More than 450 people are killed each year in the United States due to icy conditions on 11 roads (icyroadsaftey.co, 2015) of which more than 10% of these deaths are caused by accidents 12 over icy bridges. Due to this, many innovative systems have been designed and used to prevent 13 bridge icing. Most of these systems either use heat sources to heat the bridges’ surfaces or 14 chemical spray to melt the ice that forms over bridges. Unfortunately, these systems are usually 15 costly and require regular maintenance. Many researchers contributed bridge icing to the fact that 16 bridges are suspended above ground resulting in bridge surfaces to freeze before adjacent roads, 17 thus bridge decks lose heat from both the top and bottom surfaces while roads gain some heat 18 from their contact with the ground. However, field monitoring and building simulation showed 19 that the thermal properties of bridge surfaces are the true determining factor as to why bridges 20 freeze before adjacent roads. Furthermore, icy bridge surfaces become dangerous when 1) the 21 bridge’s surface reaches freezing point before adjacent roads, and 2) the existence of water or 22
GSTF Journal of Engineering Technology (JET) Vol.5 No.1, 2018
© The Author(s) 2018. This article is published with open access by the GSTFDOI: 10.5176/ 2251-3701_5. 1.109
snow over bridges when adjacent roads are dry (preferential icing). This research presents 23 literature review related to bridge freezing. The research also used field observation of a 175-mile 24 highway section during a snowstorm to investigate icing conditions over bridges. This research 25 revealed that while bridges might freeze before roads during early night hours, dangerous icing 26 formation over bridges occurs when snow is shoveled against the bridges’ parapets after 27 snowstorms. Thus, when air temperature rises above freezing, the snow melts and the water runs 28 over the bridges’ surfaces. When temperature drops again below freezing later at night, water can 29 freeze over bridges and create dangerous icy conditions. This research suggests that a 30 combination of applying paint with higher absorptive and lower emissive materials over bridges, 31 along with better snow removal practices, will reduce the dangerous icy conditions over bridges 32 significantly.