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Street cleaning

Effectiveness of road surface cleaning 

Studies into the effectiveness of street cleaning activities found that mechanical sweeping combined with water flushing achieved reductions of >90% in deposited dust loads on the road. The results also indicate that street washing is an effective mitigation technique of reducing ambient kerbside concentrations PM10 particulate matter concentrations with a measured reduction of 7-10%.

Mechanical broom sweepers are more effective at picking up the larger particles (>1000-125 um) whilst regenerative air sweepers are recommended for finer particles (< 100um). A number of factors influence the effectiveness of these street sweepers for the removal of dust sediments; these include environmental factors (climate, season) type of vehicle (sweeping mechanism), particle size and loadings, sweeping frequency and timing, surface type and moisture.

A combination of sweeping followed by washing is a reliable practice to mitigate PM emission from resuspension on a paved road.

Where there is a higher loading, such as in the proximity of demolition and construction activities it may be best to use a tandem operation, where the streets are first cleaned with a mechanical street cleaner to remove the larger particles, followed by a regenerative-air street cleaner to remove finer particles.

One area where there seems to be no research is the effectiveness of street cleaning activities and the condition of the street surface. In areas where there is a high volume of heavy vehicles passing over the public highway there is often visible signs of wear, fracturing and damage to the road surface which would almost certainly reduce  the ability of mechanical street cleaners to clean efficiently. Consideration should therefore also be given to the condition of the road surface outside the site boundary when assessing the potential impacts of street cleaning and re-surfacing may be required to allow the cleaning process to be effective.

Many on-site roads and haulage routes across demolition and construction sites are temporary and therefore have an unmade road surface. Studies on the effect of vehicle characteristics on unpaved roads have found that the magnitude of emissions was controlled primarily by vehicle speed and vehicle weight, both of which had a linear effect on the emissions, this suggest that the emissions are linearly dependant on a vehicle'™s momentum. Other physical characteristics of the vehicles (e.g. the number of wheels, undercarriage, area, height) did not appear to heavily influence the emissions.

Controlling vehicle speed on unmade roads may therefore be a simple method of reducing emissions.