Road milling helps to fix cracks and other imperfections in asphalt pavement. It also recycles the old asphalt into a new surface, cutting the costs of creating new asphalt.
Airborne dust generated by asphalt pavement milling machines can contain respirable crystalline silica. The evaluated ventilation controls on two different half-lane and larger asphalt pavement milling machines worked well for most of the evaluation shifts but were ineffective during three shifts when the wind blew dust back toward the operator and ground worker.
Road milling creates airborne dust containing silica, posing health hazards to construction workers. Using ventilation and water-spray controls can reduce workers’ exposure to this dust.
NIOSH worked with members of the Silica/Asphalt Milling Machine Partnership, including paving contractors, equipment manufacturers, unions, and government agencies, to develop best practice engineering control guidelines that address exposure to respirable silica during asphalt pavement milling on highway construction projects. This 79-page document also includes an appendix with a daily dust control checklist.
The evaluation of the engineering controls consisted of collecting full-shift personal breathing zone (PBZ) air samples from an operator and a ground worker on two different milling machines manufactured by two companies.
The evaluation showed that ventilation controls alone or combined with water-spray controls could consistently lower PBZ air exposure levels below the NIOSH recommended exposure limit (REL) for both occupations. Unfavorable wind conditions were present on three of the 21 evaluated shifts, but this did not significantly impact exposures.
Personal Protective Equipment (PPE)
Personal protective equipment (PPE) refers to clothing, gear, or other items worn to reduce the risk of injury. In workplaces where elimination, substitution, engineering, and administrative controls are not possible or practical, PPE is used to help protect workers from exposure to hazards. A PPE program should include a hazard assessment and training for employees on using, selecting, and maintaining PPE.
Body protection includes heat-resistant gloves and safety vests to prevent burns, electrical shock, and chemical exposure. Eye protection must fit properly and include lenses inspected for defects. Face shields should be free from dents and scratches. Head protection includes a hard hat and a harness that has been checked for snags.
Employees should never be allowed to skip wearing PPE for jobs that only take a few minutes. Even when PPE is protecting them, accidents can happen quickly.
Working with Machinery
Milling is noisy and requires trucks, special machinery, and portable lights. It may disrupt traffic for several days, so it is typically done at night to reduce inconvenience.
Airborne crystalline silica dust from milling asphalt pavement has been shown to put workers at risk of respiratory illness.
The milling process scrapes the existing surface layer of the road and places it into a large, rotating drum with carbide cutters that grind the asphalt into a coarse powder. This is then loaded onto a conveyor belt.
Unlike cold-milling, where excess material can be reused in road construction, the millings produced from the hot-milling process are recycled back into fresh asphalt as aggregate. This conserves valuable resources and helps protect the environment by preventing waste from ending in landfills. Moreover, it is less expensive than mixing and producing completely new asphalt.
A properly functioning traffic control system directs vehicular traffic to avoid road closures or restrictions due to construction projects, special events, or accidents. It can also help to alleviate traffic congestion caused by an unexpected influx of drivers into the area.
In some cases, a traffic management strategy can be improved by giving priority treatment to high-occupancy passenger modes like buses and carpools on congested expressways and motorways. This can be done by dedicating a dedicated lane for such vehicles to bypass traffic queues at intersections and on-ramps.
Traffic control includes the placement or erection of signs, signals, and pavement markings that meet the Manual on Uniform Traffic Control Devices standards. It also encompasses using flaggers and other personnel to regulate, warn or guide traffic. These devices are used to communicate messages to traffic participants, including the location of a road restriction, lane closing, or speed limit.
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