DRAFT 

Near-road Guidance Document – Outline 

1. Introduction – This includes objectives of document, summary of content, and references 

the preamble/rulemaking. As part of the objectives, we will include language on the 

interest in balancing required monitoring with multi-pollutant monitoring objectives. 

We will also note: 1) CASAC AAMM feedback and, 2) information on and from nearroad pilot efforts. 

2. Background – This includes some literature review and specifies what is required in the 

regulation text to site near-road stations. Given the abundance of literature on this 

subject, the literature review should focus on identifying the locations and parameters 

associated with where the maximum concentration occurs (from a multi-pollutant 

perspective – i.e., for NOx, CO, PM, etc – how they’re the same or different). 

3. Identifying Candidate Near-road Site Areas 

a. Information Collection – Identifying what resources are needed, where they can 

be found, and what those data can be used for. 

b. Ranking Roads by AADT – Using AADT to focus the site selection process 

c. Other Candidate Near-road Site Considerations 

1. Fleet Mix (notably numbers of heavy-duty trucks/buses) 

2. Roadway Design 

3. Congestion Patterns/Level of Service (LOS) 

4. Terrain 

5. Meteorology 

6. Population Density/Characteristics (e.g. SES) 

4. Modeling – How modeling can be used to supplement the near-road siting process 

5. Monitoring - How saturation and/or mobile monitoring can be used to supplement the 

near-road siting process 

6. Near-road Site Selection 

a. Safety 

b. Logistical Considerations 

c. Collaborating with other government agencies 

d. Physical Site Characteristics (e.g. distance, terrain, roadway configuration) 

7. Recommended Near-road Site Documentation – This includes recommendations on what 

to include in annual monitoring network plans and the creation of an “NCore-type” site 

characterization document for each permanent near-road monitoring station. 
DRAFT – 8/24/10 

Near-road Monitoring Pilot Study Objectives & Approach 

 In January of 2010, the EPA promulgated monitoring requirements (see attached pdf of 

the Federal Register for the Primary National Ambient Air Quality Standards for Nitrogen 

Dioxide; Final Rule, with revised monitoring language beginning on page 6435 of the notice) in 

support of the revision to the primary NOX National Ambient Air Quality Standards (NAAQS). 

As part of the rulemaking, certain state and local air agencies are required to operate near-road 

NO2 monitors, which are defined in 40 CFR Part 58, Appendices D and E. As part of this 

rulemaking, in response to public comment, EPA committed to creating near-road monitoring 

guidance materials which would be supplemented by a near-road monitoring pilot study to assist 

state and local air monitoring agencies in the implementation of required near-road monitoring 

stations. This document is intended to present and elaborate upon the primary objectives for the 

near-road monitoring pilot study. EPA intends for this pilot study to provide real-world 

experience in near-road monitoring implementation and also inform the forthcoming near-road 

monitoring guidance documentation. 

Pilot Objectives

The primary objective of the near-road monitoring pilot is to allow EPA, state, and local air 

monitoring stakeholders to evaluate, improve, and document the near-road monitor siting 

process. This objective encompasses the main process that state and local air agencies will have 

to execute when selecting and installing every required near-road monitor. As a result, pilot 

participants are gathering experience that can then be translated and communicated to all state 

and locals who will be going through this process in the near future. The pilot study process may 

provide clarity or answer the following: 

1. State and local agencies must consider fleet mix, roadway design, congestion patterns, 

terrain, and meteorology in the site selection process. Is there a relative priority amongst 

these factors? Should (could) the near-road monitoring pilot inform whether there are 

mechanisms by which to prioritize or ‘weight’ these factors in the site selection process? 

a. For example, how may a state or local agency utilize fleet mix information (which 

quantifies passenger car and heavy-duty truck volumes on individual road 

segments that will likely affect pollutant emissions differently) in their site 

selection process? 

b. What other different types of data might be available to states (e.g., Annual 

Average Weekday Traffic, Level of Service, etc.), how current is such data, and 

what do they mean, or, how are they useful? 

2. What approach should be used to balance between strictly satisfying minimum 

monitoring requirements (such as those for near-road NO2 monitors) and serving multipollutant monitoring objectives? A prime example includes evaluating how near-road 

monitors might be sited in a way to accommodate monitoring in a location of greatest 

interest/need for NO2, CO, and PM2.5. 
3. Can the pilot be supportive or informative to modeling needs, and/or can the pilot be 

supplemented by existing modeling capabilities? 

4. How effectively do the factors and available data described above support the 

identification of the maximum concentration location(s) available within a CBSA? 

a. What is the likely variation between maximum concentrations expected at the 

candidate locations identified using the above factors? How can a state or local 

agency utilize modeling and/or saturation monitoring techniques to further 

characterize candidate near-road locations? 

5. How will states mitigate issues on worker/traffic safety in near-road site selection, 

installation, and on-going operations? 

a. E.g., will air agencies need to ensure that monitoring stations are placed behind 

guardrails, or that they will need to work to have guardrails installed as 

appropriate near their near-road monitoring stations? 

b. E.g., what are any given state’s existing set-back rules? Are there issues with 

driver sight lines because of a monitoring station? 

6. What other government agencies will state and local air agencies need to communicate or 

collaborate with to achieve success in the selection and installation of near-road 

monitoring stations? 

7. Can the pilot suggest an approach by which state and local agencies, and EPA, can verify 

that the most logical and appropriate sites are being selected for the permanent near-road 

monitoring stations where AADT, fleet mix, roadway design, congestion patterns, terrain, 

and meteorology have been considered? 

Pilot Study Approach

The pilot study objectives can likely be met with a two-pronged approach. The first prong 

could be considered as a quasi-saturation monitor based evaluation, specifically to look at how a 

city could evaluate the effects of fleet mix, roadway design, congestion patterns, terrain, and 

meteorology on pollutant concentrations within their particular CBSA. The second prong could 

focus on the selection and installation of permanent near-road monitoring stations in at least two 

urban areas, using information gained as part of the first prong. Between these two prongs, EPA 

believes that all of the questions above, as part of the pilot objectives, and questions relating to 

guidance document preparation will be addressed to some degree. The data collected in the 

permanent pilot sites and the saturation monitoring studies should be analyzed to meet the pilot 

study objectives. 

The first prong, which may inform the second prong, could focus on deploying 4 or more 

saturation type monitoring “packages” (where a “package” would be mountable, mobile, or 

otherwise easy to deploy multi-pollutant measurement devices) along different road segments in 

an area to more directly ascertain how one or more of fleet mix, roadway design, congestion 

patterns, terrain, and meteorology may affect pollutant concentrations. Subsequently, the 
information extracted from this pilot may have more useful information 1) where permanent 

stations part of the prong 2 of the pilot study may be placed, and 2) to provide more information 

to states on exactly how they can account for all of the above mentioned considerations in their 

site selection process. This prong of the pilot may be accomplished with non-FRM/FEM 

methods that are pole-mountable or allow for mobile monitoring. There are passive devices and 

semi-continuous analyzers available that may be appropriate to use in this prong of the pilot. 

The near continuous methods would be most desirable since the revised NAAQS is a 1-hour 

standard and intended to protect against 1-hour peak exposures. However, on a cost basis, 

passive methods could allow for the number of segments that could be evaluated at one time to 

be significantly increased. Under the guise of using four or more near continuous monitoring 

method packages, one specific way to place the individual monitoring packages to address pilot 

objectives could be to purposefully place monitor packages at roads with specific characteristics 

including: 

 At the highest AADT segment in an area. 

 At the road segment with the highest number of heavy-duty truck/bus counts. 

 At a road segment with more unique roadway design, congestion pattern, or terrain. 

 If feasible, at a lower AADT segment with a similar fleet mix, roadway design, 

congestion, terrain, and meteorology as the top AADT road segment. This package, 

compared to the first road segment, could potentially isolate the impact of AADT on 

concentrations between two road segments. 

The second prong of the pilot would focus on establishing long-term near-road monitoring 

stations that satisfy minimum monitoring requirements resulting from the recent NOX NAAQS 

revision. This would include the overall process of identifying a pool of candidate near-road 

sites and subsequently selecting a site and installing the monitoring station. There are options on 

what the selection criteria should be for the cities installing a permanent near-road monitoring 

station. Therefore, this prong may want to try to use information gained from prong 1 of the 

pilot study, or, if possible, focus on urban areas that have no roads with outstanding 

heterogeneity with respect to fleet mix, roadway design, congestion patterns, terrain, and 

meteorology in selecting where permanent type sites may go. Of such urban areas, other metrics 

for consideration include: 

 Large versus small urban areas – Smaller urban areas (< 2.5 million) are only required to 

have one near-road site. Do they have tougher decisions to make than a larger urban area 

with regard to how to treat variances in fleet mix or any of the other ‘considerations’ that 

must be made? Should the pilot include a city that is relatively small, but represents the 

only urban area in a state that will have a near-road monitor? Should this proposed first 

prong include one large and one smaller urban area? 

 Terrain and meteorology – Urban areas with more varied and complex terrain or 

meteorology may provide an informative experience to share with other states versus 

urban areas with rather flat or unremarkable terrain or meteorology. 

 Urban areas where the state or local air agency may or may not have local/state support, 

such as a DOT amenable to cooperate in aiding site installations. 

 An urban area with an operational NOX analyzer that is considered representative of the 

broader urban background. This would provide information on how much higher nearroad concentrations are when compared to relative background concentrations in order to 

identify the road’s contribution. 
 An urban area with a DOT or Metropolitan Planning Organization (MPO) with detailed 

traffic information and project modeling results. 

Near-Road Site Implementation and Documentation

The pilot study will also provide information and documentation that will assist states in the 

implementation of their near-road monitoring sites. These include: 

 Data Collection – Where can traffic and other pertinent data be found, which data sources 

were and were not useful, and what obstacles were encountered? 

 Candidate Site Selection and Data Analysis – How was the data evaluated and interpreted 

in order to select the candidate sites, and how could this process be refined and 

improved? 

 Near-Road Site(s) Selection – When evaluating candidate sites, what unforeseen 

obstacles were encountered, how accurate were the data collected, and what difficulties 

were encountered in establishing the site? 

 Approvals and Installation – After selecting the site location(s), what approvals were 

needed and how cooperative were state and local agencies and organizations? Were any 

obstacles encountered when installing the site, such as safety or electricity access? 

 Operation and Maintenance – During the time of operation, were any issues or difficulties 

encountered such as safety, inconsistent operation, access limitations, etc.?