Beginning at approximately 3 p.m. today, crews from the City of Tucson Department of Transportation (TDOT) Streets and Traffic Maintenance Division will initiate Operation Freeze in preparation of freezing overnight temperatures. Operation Freeze is put into place to make sure City bridge decks are free of ice and safe for motorists to drive over.
During Operation Freeze, City crews place “Wet Road Ahead” signs at bridge entrances and spray magnesium chloride on the bridge decks. Magnesium chloride lowers the freezing temperature of water and prevents ice from bonding on a roadway. A light coating of magnesium chloride produces no negative effects on ground water, surface water or vegetation. Magnesium chloride is an effective ice suppressant agent lasting for approximately 10 days. Rainfall diminishes its effectiveness.
When temperatures warrant, 58 City bridge decks will be sprayed and monitored throughout the evening and into the early morning to make sure ice has not formed at the crossings. Motorists should to be aware of crews working around the bridge deck crossings and drive with caution when the possibility of ice exists on the roadways.