LTC 318-2008 51st Street and Blackhawk Avenue Intersection'EC.;t=.~j`=~
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OFFICE OF THE CITY MANAGER
NO. LTC#318-2008 LETTER TO COMMISSION
TO: Mayor Matti Herrera Bower and Members of the City Commission
FROM: Jorge M. Gonzalez: City Manager ~_,.- ~
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DATE: December 8, 2008 ~ ~ -
SUBJECT: 515' Street and Blackhawk Avenue Intersection
BACKGROUND
The purpose of this Letter to Commission (LTC) is to provide you with the status of a request by
residents for the installation of stop signs at the intersection of 515' Street and Blackhawk Avenue.
According to residents, motorists speeding on 515' Street has been an increasing problem, that has
created a dangerous situation for pedestrians in the neighborhood, as well as made it more difficult
for those traveling south on Blackhawk Avenue to enter the roadway on 51'' Street. Residents
believe that athree-way stop would result in traffic calming and would bring order to the intersection
movements.
ANALYSIS OF EXISTING CONDITIONS
City staff forwarded the request to the Miami-Dade County Public Works Department, Traffic
Engineering Division (the County). The County then initiated a study to evaluate existing traffic
conditions and to determine the feasibility of implementing either an °All Way" stop control or
providing for traffic calming devices at this location.
An "All Way' stop control could be installed at the intersection if certain traffic conditions as defined
in the Federal Highway Administration's Manual on Uniform Traffic Control Devices (MUTCD) are
met. These traffic conditions include the following: approximately equal vehicular volumes on the
intersecting roads; and these volumes should be a minimum of 3,000 vehicles per day on the major
street and 2:000 per day on the minor street.
The speed and volumes were measured by the County during a recent 24-hour period and the
results are indicated in Table 1.
Table 1. Existing Traffic Volumes and Speed
Street Name and Direction 8- S~Percentile Speed Volume
(Miles per Hour (MPH Vehicles per day)
51 a t, Eastbound 30 1162
51'' Street, Westbound 30 1168
Blackhawk Avenue. 29
Southbound I ~
The traffic data collected revealed that the traffic volumes on 515 Street and Blackhawk Avenue are
far below the minimum required for the requested stop signs. Furthermore, a search of crash reports
for the last three (3) years revealed that there were no reported crashes at this intersection. As such,
the County has not approved the installation of "All Way'' stop control signs at this location.
LTC
December 4, 2008
51s' Street and Blackhawk Intersection
Page 2 of 2
TRAFFIC CALMING
In order to install traffic calming devices, the street or road must meet certain minimum criteria
established by the County's Public Works Department. Minimum traffic volumes must be greater
than 150 vehicles per hour or 1500 vehicles per day: and the 85'" percentile speed, which is defined
as "the speed that is set by most municipalities to separate the bottom 85% of vehicles from the top
15%". The theory behind this is that most drivers will travel at a speed that is reasonable and
prudent for a given roadway segment. Most U.S. jurisdictions report the 85% speed as the best
indicator of the prevailing or reasonable speed. In this case in order to warrant traffic calming, the
85% percentile must be at least 10 MPH greater than the established speed limit of the road.
As shown in Table 1 the traffic volume is less than 1,500 per day and the 85°i percentile does not
exceed by 10 MPH of the 30 MPH street posted speed limit. Therefore, the County did not approve
installation of traffic calming devices. However, should conditions change in the future, the City will
reconsider the installation of traffic calming devices or other traffic control signs.
RECOMMENDATION
At this time, the County has not approved the installation of stop signs or other traffic calming
measures at the intersection of 51'` Street and Blackhawk Avenue. The City will continue to
coordinate with the County in an effort to monitor the performance of the intersection in the future
anyyd//~~LLt~~jo,~~{{re~c//oJ,mmend appropriate solutions if necessary.
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