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Road Environmental Sustainability

Environmental Sustainability Overview

On environmental sustainability, two factors tend to dominate the conversation when it comes to road freight — that is the impact of truck operations upon 1) air quality and 2) hazardous material spills.

Air Quality

Air quality continues to be a key criterion for OKI in making decisions for all its transportation planning and investments. The National Ambient Air Quality Standards (NAAQS) are set by the U.S. Environmental Protection Agency (EPA) to protect public health and the environment. Of the five monitored air pollutants (carbon monoxide (CO), nitrogen dioxide (NOx), particulate matter (PM2.5), sulfur dioxide (SO2) and ozone), a large portion of the OKI region was recently considered a “nonattainment” area for ozone. However, in 2022, the EPA found that the OKI region had attained the ozone standard. Attainment means ozone concentrations meet the NAAQS. Vehicle emissions are a major contributor to ozone and PM2.

To determine the impact trucks have on the region’s emission levels, OKI calculated truck emission data for six air pollutants: carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NOx), particulate matter (PM2.5), sulfur dioxide (SO2), and volatile organic compounds (VOC). Emissions were based on truck vehicle miles traveled (VMT) for Federal Highway Administration FHWA vehicle classes six to 12.

Truck Emissions as a Percent of All Vehicle Emissions

In transportation planning, it is well established that trucks generate much higher NOx and PM2.5 emissions than other motorized vehicles, based on vehicle miles traveled (VMT). OKI’s analysis estimated that trucks contribute about 66 percent NOx and 75 percent PM2.5 of the region’s 2019 total on-road mobile emissions. Boone and Kenton counties report even higher 2019 truck percentages of NOx emissions at about 74 percent and 73 percent, respectively. Regarding PM2.5 truck emissions, all three OKI northern Kentucky counties report percentages higher than the region — Boone (83 percent), Campbell (82 percent), and Kenton (85 percent).

In comparison to NOx and PM2.5, trucks account for only about a third of all CO2; eight percent of all CO; 16 percent of all SO2; and 11 percent of all VOC emissions in the region.

Truck Delay as a Contributor to All Vehicle Emissions

As discussed on the Road Mobility and Reliability webpage, trucks are experiencing high levels of travel time delay in both the AM and PM peak periods. OKI’s examination of truck delay on the region’s total vehicle emissions showed the impact to be quite small. Although trucks, like all vehicles, experience delay on our region’s roadways, the percent of truck emissions caused from delay comprises a small percentage of the overall total regional vehicle emissions (cars and trucks). Even NOx and PM2.5 levels from truck delay account for only about 5 percent of the region’s total emissions in these two categories. Across all six air pollutant categories, Hamilton County experiences the highest percentages of truck emissions from truck delay.

Truck Delay as a Percent of Total Truck Emissions

When emissions caused by truck delay are examined as a percentage of total truck emissions, not surprisingly, it is higher than the percentage from all vehicle emissions. However, except for VOC levels in Butler and Hamilton counties, air pollutants originating from truck delay comprise 10 percent or less of all 2019 truck emissions. The greatest source of truck emissions occurs from the high level of vehicle miles trucks travel in, out, within, and through the OKI region. A case in point is the Ohio Department of Transportation’s (ODOT) finding during the Brent Spence Bridge’s 41-day closure in 2020. It resulted in more than 13,250 trucks per day being rerouted, which increased truck trips by about 13 minutes and the median trip distance by about 17.6 miles. ODOT estimated that the closure resulted in around 160 tons of additional emissions (HC, CO, NOx, PM2.5) added to the environment. (Source: Ohio Department of Transportation (ODOT). Transport Ohio, Existing Freight System Performance, Working Paper 5. (2021).

Road HAZMAT Incidences

Hazardous Material (HAZMAT) incidents are reported for highways, air cargo and rail. Truck-related HAZMAT incidences account for almost all incidences reported for the past two decades — with one exception. In Boone County, air cargo-related HAZMAT incidences at the Cincinnati/Northern Kentucky International Airport (CVG) are more common than truck-related events in the county. Truck-related HAZMAT incidences have declined as a percentage of all Boone events over the past several years, which is due to the rise in air cargo activity at CVG.

For the region as a whole, the number of road-related HAZMAT incidences has increased by more than 145 percent over the past two decades. Hamilton County shouldered the greatest number of road HAZMAT incidences between 2001 and 2010. In the most recent decade, Hamilton’s share of road HAZMAT incidences has decreased and been spread more evenly with Butler and Kenton counties.

Campbell, Clermont and Dearborn counties collectively report fewer than 10 HAZMAT incidences over the past two decades. Those that have occurred have been road related. No fatalities were reported for any HAZMAT incident over the past 20 years in the OKI region.

Road HAZMAT Released

Just as the number of truck HAZMAT incidences has risen dramatically over the past decade, so too has the amount of HAZMAT released from trucks. This amount has increased more than 256 percent during the 20-year period while the total amount from all modes decreased 18 percent. Over 69 percent of the truck HAZMAT released in the past decade occurred in Butler County. (Source: United States Department of Transportation, Pipeline and Hazardous Materials Safety Administration (PHMSA) (2010 and 2020). Hazardous Materials (HAZMAT) Incident Report. [Data set].)

Road HAZMAT Damages

Once again, due to the rise in road HAZMAT incidences overall and as a percent of all HAZMAT events, the cost of HAZMAT damages has also increased from $1.2 million for the decade ending in 2010 to over $2.3 million in the decade ending in 2020. Butler and Hamilton counties account for the greatest costs from road HAZMAT incidences, at about 37 percent and 38 percent of the mode’s total, respectively. The HAZMAT costs for each county can almost entirely be attributed to road events, except for Hamilton County, where rail HAZMAT costs account for almost a third of its total.

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