El Dorado County General Plan
versus El Dorado Hills traffic
A place
that could be superb if not for traffic
This section looks at traffic issues in connection with two upcoming
ballot measures. One is an initiative to amend the El Dorado County
charter to prohibit adoption of a General Plan which produces excessive
traffic congestion. The other is a referendum on the 2004 General Plan.
Index to
sections on this and other web pages:
Basic problem
El Dorado County's 2004 General Plan assures that the already-serious
traffic problems in El Dorado Hills will become MUCH worse.
The Board of Supervisors, against the
recommendation of the Planning Commission, adopted the Base Alternative
with a Land Use element that maximizes housing growth, and consequently
maximizes traffic growth. Proponents may claim that it will only
double traffic volume; opponents say that it will triple traffic
volume. Either case is the basis for a traffic disaster.
The Board of Supervisors, against the recommendation of the consultants
(Fehr and Peers) retained to evaluate traffic impacts, reduced future
roadway infrastructure development.
Both land use and traffic infrastructure planning funnel almost all
commute traffic through US 50 and specifically through El Dorado Hills.
Topology of the network of roadways is rural in character and has
inadequate arterial alternatives.
El Dorado Hills already has LOS F
(the Level Of Service at which roadway capacity is exceeded) on US 50
and on arterials connecting to US 50 (El Dorado Hills Blvd. and Latrobe
Road). EDH already has at the level of traffic delay forecast as
the average for the entire county in 2025, and the General Plan assures that the delay WILL get worse.
The most
important single relationship from traffic engineering for this
situation is:
VHD
= 
where VHD is Vehicle Hours of Delay
alpha is a
coefficient that depends on particular traffic circumstances
beta is a
second situation-specific coefficient that typically is about
4
V is traffic volume, the
demand for roadway capacity
C is
actual roadway capacity
LOS F occurs when V/C is at least 1. Vehicle Hours Delay grows in proportion to
the fourth power of V/C. If V/C
doubles, vehicle hours of delay increases by a factor of 16. The
General Plan's Environmental Impact Report in fact projected that at
buildout VHD will grow by about a factor of 40 relative to base year
delays. 1999 was the year used as the base year. Traffic impacts
will be higher in El Dorado Hills than in the rest of the county due to
focusing commute traffic onto US 50.
The 2004 General Plan permits growth
of V (volume) on this segment of US 50 by a minimum of 200%. It plans
to increase C (capacity) by about 35% to 40% by expanding the freeway
to 8 lanes, but all sources including Supervisor Helen Baumann
acknowledge that there is no realistic expectation for widening to 8
lanes.
Here's what this means for roads such as Green Valley Road and Highway
49, as shown in one graph excerpted from the U.S.
Department of Transportation's Model
Validation
and Reasonableness Checking Manual. A second web reference
with more detail on this modeling is Delay-Volume Relations
for Traffic Forecasting: Based on the 1985 Highway Capacity Manual,
in the section on Delay Functions for
Uncontrolled Road Segments. All of this information is on
the Federal Highway
Administration web site.
Figure 7-1
Example Travel Times and Speeds Using BPR Function
(color highlighting and color
legend at bottom added by this author)
Source: http://tmip.fhwa.dot.gov/clearinghouse/docs/mvrcm/ch7.stm
Model Validation
and Reasonableness Checking Manual
Traffic
Model Improvement Program
U.S. Department
of Transportation
Original copy of this graph is at http://tmip.fhwa.dot.gov/clearinghouse/docs/mvrcm/images/fig7-1.gif
The area highlighted in yellow corresponds to the range of conditions
currently seen by this author in peak periods and at times in off-peak
periods. The area highlighted in orange is a conservative projection of
what this will become when county and city population grow to the
extent provided for in the 2004 General Plan and in existing Specific
Plans, assuming that V/C will double.
Current observations are generally consistent with the higher value of
alpha (1.0) graphed by DOT. Improvements in the El Dorado Hills/US 50
interchange and in specific local arterials can be expected to cause a
shift toward a lower value of alpha. Whether its value may drop to .15
is an open issue. Either case is extremely troublesome, producing
Mini-gallery
-- photos of current traffic conditions
Photos were taken from several vantage points between 3:00 and 4:00
p.m., still two or three hours earlier than typical maximum traffic. US
50 eastbound, El Dorado Hills Blvd. southbound, and Latrobe Road
northbound were already operating at LOS F. LOS F means that
through traffic is slow and traffic speed is unstable, often reaching a
standing stop; delays at intersections are excessive and surface
streets can be in gridlock.
US
50, less than 1 mile west of EDH Blvd. / Latrobe Road interchange
US
50, also showing traffic on westbound onramp
US
50 looking north toward interchange, EDH Town Center in background
Latrobe
Road at US 50, with EDH Blvd. offramp (spiral, partly behind trees)
EDH
Blvd., looking north from US 50
EDH
Blvd. north of US 50, viewed from southwest
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