90 LOS is defined in terms of the average total vehicle delay of all movements through an intersection. Vehicle  delay is a method of quantifying several intangible factors, including driver discomfort, frustration, and lost  travel time. Specifically, LOS criteria are stated in terms of average delay per vehicle during a specified time  period (for example, the PM peak hour). Vehicle delay is a complex measure based on many variables,  including signal phasing (i.e., progression of movements  through the intersection), signal cycle length, and  traffic volumes with respect to intersection capacity.  65$_{ }$ “(i) New highway projects that have a significant number of diesel vehicles,  and expanded highway projects that have a significant increase in the number  of diesel vehicles; (ii) Projects affecting intersections that are at LOS D, E, or  F with a significant number of diesel vehicles, or those that will change to  LOS D, E, or F because  of increased traffic volumes from a significant  number of diesel vehicles related to the project; (iii) New bus and terminals and transfer points that have a significant number of diesel vehicles  congregating at a single location; (iv) Expanded bus and rail terminals and  transfer points that significantly increase the number of diesel vehicles  congregating at a single location; and (v) Projects in or affecting locations,  areas, or categories of sites which are identified in the PM 10  or PM 2.5  “…In cases other than those described above, the demonstrations required by  § 93.116 may be based on either:(i) Quantitative methods that represent  reasonable and common professional practice; or  (ii) A qualitative  consideration of local factors, if this can provide a clear demonstration that  the requirements of § 93.116 are met.”  Furthermore, 40 CFR 93.123(a)(2) states:  “(i) For projects in or affecting locations, areas, or categories of sites which  are identified in the applicable implementation plan as sites of violation or  possible violation;(ii) For projects affecting intersections that are at Level-of- Service (LOS) 90  D, E, or F, or those that will change to  LOS D, E, or F  because of increased traffic volumes  related to the project;  (iii) For any  project affecting one or more of the top three intersections nonattainment or maintenance area with highest traffic volumes, as identified  in the applicable implementation plan; and (iv) For any project affecting one  or more of the top three intersections in the nonattainment or maintenance  area with the worst level of service, as identified in the implementation plan.”  − As stated in 40 CFR 93.123(a)(1) a quantitative CO hot -spot analysis should  be considered for the following types of projects:  − 40 CFR 93.123(b)(1) defines the projects of  air quality concern  that require a  quantitative PM$_{10 }$and PM$_{2.5 }$hot-spot analysis as:  • Determine whether project/action is in need of a quantitative hot -spot analysis. A hot - spot analysis is required only for projects of local  air quality concern. The following  describes the types of projects/actions that might require a hot-spot analysis for CO, PM$_{10 }$ and PM$_{2.5}$, respectively:  Aviation Emissions and Air Quality Handbook 