B.3. - ASSESS TRAFFIC VOLUMES

B.3.1.   Existing Traffic

A.

Roadway Traffic Volumes/Traffic Counts. Current A.M. and P.M. peak hour traffic counts as specified by the ECM Administrator shall be obtained for the roadways within the study area for one, non-holiday Tuesday, Wednesday, or Thursday. Each peak hour count shall be conducted over a two-hour period and shall include fifteen (15)-minute count data to clearly identify the peak hours.

Weekend counts and average daily counts on local roadways may also be required where appropriate when requested by the ECM Administrator. The DOT or CDOT average weekday traffic (AWT) counts may be used when available. Pedestrian counts and bicycle usage should be obtained. Vehicle classification counts may be required.

In any case, these volumes shall be no more than one year old (from the date of application submittal). The source(s) of each of the existing traffic volumes shall be explicitly stated. Summaries of current traffic counts shall be provided. The ECM Administrator may require the use of seasonal adjustment factors depending on when data was collected and if the project is considered to be in an area of higher risk for lower levels of services (i.e., Tourism).

B.

Intersection LOS. A.M. and P.M. peak hour intersection LOS shall be determined for the existing collector and arterial signalized and unsignalized intersections within the transportation network to be studied. The analysis shall use procedures described in the Highway Capacity Manual. Factors for intersections will be by approach and those used for roadways will be by facility unless otherwise directed by the ECM Administrator.

1.

Existing and Short-Range Horizon. Use calculated peak hour factors or 0.85, whichever is higher, and

2.

Long-Range Horizon. A peak hour factor of 0.95 may be used for the Long-Range Horizon. Greater values may be used if approved by the ECM Administrator.

C.

Roadway Links. Roadway links shall be analyzed. Acceptable maximum traffic volumes allowed for the specific class of roadway are shown in Table B-1.

Table B-1. Threshold Capacity

Facility Type	Lanes	ADT Threshold Capacity (Urban/Rural)
Local (low volume)/Local (rural)	2	300/750
Collector-Non-Residential	2	20,000
Local (urban)/Minor Collector (rural)	2	3,000/1,500
Major Collector	2	10,000/3,000
Minor Arterial	4	20,000/10,000
Principal Arterial (4-lane)	4	40,000/40,000
Principal Arterial (6-lane)	6	40,000/40,000
Expressway (4-lane)	4	48,000/48,000
Expressway (6-lane)	6	48,000/48,000

 

B.3.2.   Background Traffic

A.

Short-Range Volume Projections. The traffic forecast for the short-range planning horizon shall be the sum of existing traffic volumes plus cumulative development traffic from approved land use actions (projects with reserved intersection capacity established through a certified Full TIS), plus background growth (as adjusted to avoid duplicative consideration of the identified development traffic from the approved land use already considered). The cumulative development traffic shall be based, in part, on the A.M. and P.M. peak hour and (ADT) data established and accepted from planned and approved land use actions within and near the study area. The assumed baseline surface transportation network shall reflect existing facilities (without the proposed project improvements) plus any committed improvements within the study area.

The short-range planning horizon background traffic growth rate shall be based:

• Straight line projection for the build-out year between the existing traffic volumes and the MTCP model forecast, CDOT rates;

• Historical traffic counts projected to the build-out year (at least three years of traffic data should be used for this); or

• Area-wide traffic count analysis that considers traffic volume trends in the study area's circulation system and uses proportion/extrapolation methods.

B.

Long-Range Volume Projection.  

• Straight line projection for the build-out year between the existing traffic volumes and the MTCP model forecast, CDOT rates;

• Historical traffic counts projected to the build-out year (at least three years of traffic data should be used for this);

• Area-wide traffic count analysis which considers traffic volume trends in the study area's circulation system and uses proportion/extrapolation methods; or

• Growth rate agreed upon with the ECM Administrator.

B.3.3.   Project Traffic

A.

Trip Generation Rate. Trip generation shall be calculated from the latest data contained within the Institute of Transportation Engineers' Trip Generation Manual. Other industry publications (such as the ITE Journal or other sources) may be approved by the ECM Administrator. Data limitations, data age, choice of peak hours (for the land use or adjacent roadway traffic), choice of independent variables, and choice of average rate versus statistically significant modification shall be discussed in the study when appropriate. When data is not available for a proposed land use or a modification is proposed, the Applicant must conduct a local trip generation study following procedures prescribed in the ITE Trip Generation Manual and provide sufficient justification for the proposed generation rate. This rate must be approved by the ECM Administrator prior to its use in the written study.

B.

Preliminary Land Use Assumptions. The trip generation values contained in studies submitted prior to the establishment of a site-specific development plan shall be based on the maximum number of dwelling units permitted for the approved land uses or the maximum trip generation rates for the non-residential development proposed land use action. When a TIS is being developed for a project with an established site-specific development plan, trip generation shall be based on actual dwelling unit counts and square footage(s) proposed on the final plan.

C.

Trip Generation Table. A Trip Generation Table, listing each type of land use within the site at build-out, the size and unit of measure for each land use, trip generation rates (total daily traffic, A.M. and P.M. peaks), directional splits for each in/out access, and the resultant total trips generated shall be provided. The data source shall include ITE land use code. Build-out land uses and trip generations shall be used for both the short-range and long-range planning horizons.

D.

Committed Trips/Capacity. The trip generation stated in the TIS will establish the maximum number of trips permitted entering and exiting the development. If the number of committed trips is reached prior to full occupancy, the ECM Administrator reserves the right to require from the sponsor, at the sponsor's expense, supplemental traffic analyses prior to the issuance of additional building permits. This information shall demonstrate that uncommitted capacity is available on the transportation network to serve the excessive trips, or that additional transportation mitigation improvements can be reasonably installed to maintain compliant operation with the excessive trips. If no additional capacity is available, or no reasonable mitigation conforming to the requirements of these roadway standards can be implemented, the owner shall obtain an exception from the ECM Administrator for the non-conformity or scale back the intensity of the proposed land uses as needed to achieve compliance. If the project is fully occupied and it is determined that the approved land use action's traffic exceeds that which was included in the approved TIS, the ECM Administrator is authorized to require the property to conduct additional traffic analysis and provide additional mitigation measures.

E.

Adjustments to Trip Generation. Trip-making reduction factors may be used after first generating trips at full ITE rates. These factors fall into two categories: those that reassign some portion of generated trips to the background stream of traffic, and those that remove or move generated trips. In all cases, the underlying assumptions of the ITE trip generation rates must be recognized and considered before any reductions are used in the TIS. Two specific situations will be closely reviewed. The first is when the traffic study assumes rates where the collection of mixed uses, such as at a shopping center, result in lower peak hour trips than when applying individual rates to each land use. The second is when reductions in the trip generation rates are assumed based on reductions due to travel demand management.

1.

Pass-by Trips. This first category may be considered when trips to the proposed development currently exist as part of the background traffic stream, referred to as a pass-by trip. Pass-by percentages identified in the ITE Trip Generation Manual will be considered with appropriate explanation and documentation. Pass-by traffic must remain assigned to driveways and access points, but should not be added to the background traffic stream. A technical appendix, table, or map that illustrates the re-diversion of pass-by trips is required.

2.

Internal Site Trips/ Transportation Demand Management (TDM). Analytic support documentation of internal site trips, public transportation services use, and TDM actions shall be provided to show how trip adjustments are derived. Optimistic assumptions regarding public transportation use and TDM actions will not be accepted unless accompanied by specific implementation proposals that will become a condition of approval. Such implementation proposals must have a high expectation of realization within a 5-year period after projection initiation.

F.

Trip Distribution. Trip Distribution must be documented in the TIS. It may be based on the professional engineer's judgment applied to one or more of the following: MTCP traffic volume projections, gravity model, market analysis, existing traffic flows, or applied census data. Regardless of the basis of the estimates, the procedures and rationale used in determining the trip distributions must be fully explained, documented, and approved by the ECM Administrator.

G.

Trip Assignment. The project traffic will be assigned to the roadway system according to the trip distribution. The resulting project site-generated traffic and total site traffic will be depicted on figures for each analysis horizon. These figures will include peak hour traffic volume information, plus daily traffic volume information. Separate maps or values are required when the trip distribution differs by more that 10 percent between the short-and long-range analysis horizons.

B.3.4.   Total Traffic

The total traffic projections will be determined for each of the analysis horizons identified in the base assumptions. The total traffic projections will include the existing traffic, plus the future background traffic, plus the project generated traffic. The future total traffic projections will be depicted on figures for each study year. Based upon the total traffic projections, roadway standards, and MTCP, the applicant shall provide roadway functional classification recommendations.