The model uses statistical equations and key inputs to estimate how much traffic will be on our County roadways in the future. The key inputs include roadway characteristics (such as the speed limit, number of lanes, and classification) and land use characteristics (such as the number of households that exist today and in the future).
The TDM is not available for use by the general public. The TDM requires a software license for Citilabs CUBE. Typically, transportation planners and engineers are the operators of the TDM and use it in support of transportation impact studies, fee programs, planning documents and other uses. The County does make the TDM available for use by consultants and other public agencies for specific projects. Please contact Natalie Porter at email@example.com to obtain the TDM files.
The following definitions and data provided in Table 1 below are from the Highway Capacity Manual 2010, (HCM2010 or HCM) Transportation Research Board.
LOS B: Passing demand and passing capacity are balanced. On both Class I and II highways, the degree of platooning becomes noticeable. Some speed reductions are present on Class I highways. On Class III highways, it becomes difficult to maintain FFS operations, but the speed reduction is still relatively small.
LOS C: Most vehicles are traveling in platoons. Speeds are noticeably curtailed on all three classes of highway.
LOS D: Platooning increases significantly. Passing demand is high on both Class I and Class II facilities, but the ability to pass approaches zero. A high percentage of vehicles are now traveling in platoons, with a noticeable percent time spent following (PTSF). On Class III highways, the reduction from free-flow speed is significant.
LOS E: Demand is approaching capacity. Passing on Class I and Class II facilities are virtually impossible. Speeds are curtailed, and the percent time spent following (PTSF) is more than 80%. On Class III highways, speed is less than two-thirds the FFS. The lower limit of this LOS represents capacity.
LOS F: Exists whenever demand flow in one or both directions exceeds the capacity of the segment. Operating conditions are unstable, and heavy congestion exists on all classes of two-lane highways.
LOS A: Free-flow operations. Vehicles are almost completely unimpeded in their ability to maneuver within the traffic stream. The effects of incidents or point breakdowns are easily absorbed.
LOS B: Reasonably free-flow operations. The ability to maneuver within the traffic stream is only slightly restricted, and the general level of physical and psychological comfort provided to drivers is still high. The effects of minor incidents and point breakdowns are still easily absorbed.
LOS C: Provides for flow with speeds near free-flow levels. Freedom to maneuver within the traffic stream is noticeably restricted, and lane changes require more care and vigilance on the part of the driver. Minor incidents may still be absorbed; queues may be expected to form behind any significant blockages.
LOS D: Speeds begin to decline with increasing flows, with density increasing more quickly. Freedom to maneuver with the traffic stream is seriously limited and drivers experience reduced physical and psychological comfort levels. Even minor incidents can be expected to create queuing, because the traffic stream has little space to absorb disruptions.
LOS E: The lower level represents capacity. There are few usable gaps within the traffic stream to accommodate maneuvers. Minor incidents create queuing and breakdowns.
LOS F: Demand flow exceeds capacity.
Figure 1: LOS for Freeway Segments
(Highway Capacity Manual 2010, Chapter 11, page 11-5)
LOS B: This level is typically assigned when the volume-to-capacity ratio is low and either the progression is highly favorable or the cycle length is very short. More vehicles stop than with LOS A.
LOS C: This level is typically assigned when progression is favorable or the cycle length is moderate. Individual cycle failures (i.e., one or more queued vehicles are not able to depart as a result of insufficient capacity during the cycle) may begin to appear at this level. The number of vehicles stopping is significant, although many vehicles still pass through the intersection without stopping.
LOS D: This level is typically assigned when the volume-to-capacity ratio is high and either progression is ineffective or the cycle length is long. Many vehicles stop and individual cycle failures are noticeable.
LOS E: This level is typically assigned when the volume-to-capacity ratio is high, progression is unfavorable, and the cycle length is long. Individual cycle failures are frequent.
LOS F: This level is typically assigned when the volume-to-capacity ratio is very high, progression is very poor, and the cycle length is long. Most cycles fail to clear the queue.
The following video links illustrate Levels of Service A through F at a signalized intersection. Video simulations were produced by Dave Stanek, Associate at Fehr and Peers.
LOS for a stop controlled intersection is determined by the computed or measured control delay. The LOS criteria for stop controlled intersections are somewhat different from the criteria used for signalized intersections, primarily because user perceptions differ among transportation facility types. The expectation is that a signalized intersection is designed to carry higher traffic volumes and will present greater delay than an unsignalized intersection. Unsignalized intersections are also associated with more uncertainty for users, as delays are less predictable than they are at signals.
Additional capacity in Placerville has recently been provided by Caltrans. However, as long as the three traffic signals are necessary for safe movements of city traffic, and high volumes of traffic use U.S. Highway 50, congestion within the City of Placerville will occur.
Prior to the ramp metering of the westbound on-ramp at El Dorado Hills Boulevard, which became operational in Spring of 2015, U.S. Highway 50 from the El Dorado Hills Boulevard/Latrobe Road interchange to the County line frequently operated at LOS F in the westbound direction during the AM peak hour (7:20 – 8:20 AM). Caltrans reports all other segments of U.S. Highway 50 operates at LOS E or better. However, the County’s traffic analysis using the TDM differs from Caltrans analysis results provided in the Caltrans 2014 Transportation Concept Report and Corridor System Management Plan for United States Route 50 (see Supporting Documents for the Caltrans report). Also, see the Supporting Documents for a staff memo dated 9-1-2015 to the Planning Commission which contains a discussion and documentation regarding LOS on Highway 50, including an explanation regarding why Caltrans and the County arrive at different conclusions.
Traffic count information is available in three formats: Hourly Traffic Count Reports, Annual Traffic Count Summary, and Five Year Traffic Count Summary. Traffic Operations is responsible for the collection and reporting of information. The last ten years of segment counts are posted on the Transportation Division’s website at: http://edcapps.edcgov.us/dot/trafficcounts.asp. Since a number of factors may impact count data collection from year to year (e.g., construction on neighboring roads, holidays, special events, etc.) caution should be exercised when using the data on the website for comparison purposes. The Special Projects & Materials Testing staff can be reached at (530) 642-4989.
El Dorado County does not collect traffic counts for any state highways (i.e. U.S. Highway 50, State Route 49, State Route 193) since Caltrans is responsible for maintaining information on their state highway infrastructure. For the state highway system, the County relies on Caltrans data via the Caltrans Performance Measurement System (PeMS) plus volumes that Caltrans provides. This data is available for public use at: http://pems.dot.ca.gov.
To obtain specific results of the operations of an intersection, a separate software program is required. The County has just acquired the software required to run the Micro analysis. The TDM provides the foundational information to run the more specific micro analysis at desired locations.
There are three primary levels of analysis, listed from most to least detailed:
Not necessarily. When the 20 year growth forecast has been finalized, the County will be able to run existing and future scenarios to evaluate traffic impacts from current and potential future land uses. The traffic impact evaluation of projected growth and where it occurs can then be used to determine the appropriate roadway infrastructure needs throughout the west slope of the County.
The basic calculation for TIM fees is: TIM Fee = Revenue Required (Cost of Needed Improvement) / Growth Expected (# of Units)
Here are four hypothetical examples of how changes to growth forecasts and/or infrastructure needs could impact TIM fees: