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F -35
Intersection Sight Distance
The following table shows intersection sight distance requirements for various speeds
along major roads:
Line of Sight
NUT
ITEM
14.5'Object
Hiaht
IN.E e Height
3.
e
5')
E -- SDL t SDR --
SDR = Sight Distance Right (For a vehicle making a left turn)
SDL = Sight Distance Left (For a vehicle making a right or left turn)
Height of Eye 3.5'Height of Object 3.5'
Design Speed (mph) ** 20 25 30 35 40 45 50 55 60 65 70
In Feet 225 280 335 390 445 500 555 610 665 720 775
SDR: 2 Lane Major Road
SDL: 2 Lane Major Road 195 240 290 335 385 430 480 530 575 625 670
SDR: 4 Lane Major Road
240 295 355 415 475 530 590 650 710 765 825Undivided) or 3 Lane
SDL: 4 Lane Major Road
225 280 335 390 445 500 555 610 665 720 775Undivided) or 3 Lane
SDR: 4 Lane Major Road
260 325 390 455 515 580 645 710 775 840 905Divided — 18' Median)
SDL: 4 Lane Major Road
245 305 365 425 490 550 610 670 730 790 850Divided — 18' Median)
SDR: 5 Lane Major Road
continuous two -way turn- 250 315 375 440 500 565 625 690 750 815 875
lane)
SDL: 5 Lane Major Road
continuous two -way turn- 240 295 355 415 475 530 590 650 710 765 825
lane)
SDR: 6 Lane Major Road
275 340 410 480 545 615 680 750 820 885 955Divided — 18' Median)
SDL: 6 Lane Major Road
260 325 390 455 515 580 645 710 775 790 850Divided — 18' Median)
SDL: (Where left turns
195 240 290 335 385 430 480 530 575 625 670arephysicallyrestricted)
TABLE 2 -7 INTERSECTION SIGHT DISTANCE
Source: AASHTO Green Book (See Exhibits 9 -54 thru 9 -57)
F -80
SECTION 4 - ENTRANCE DESIGN
Entrance Design Principles
Entrances are, in effect, at -grade intersections and should be designed consistent with
the intended use. The number of crashes is disproportionately higher at entrances than
at other intersections; thus their design and location merit special considerations.
Entrances should not be situated within the functional area of an intersection or in the
influence area of an adjacent entrance. The functional area extends both upstream and
downstream from the physical intersection area and includes the longitudinal limits of
auxiliary lanes.
Entrance Angle: The entrance centerline should be perpendicular to the state highway
centerline and extend tangentially for a minimum distance of 40 feet beyond the
near -side edge line. An acute angle between 60 degrees and 90 degrees may be
permitted if significant physical constraints exist. Acute angles less than 60
degrees shall require special approval of the Department.
Entrance Radius: The entrance radius should be designed to accommodate the design
vehicle expected to use the entrance on a daily basis.
Design Vehicle and Turning Radius by Land Use
Land Use(s) Served by Access Design Vehicle Radius
Office with Separate Truck Access Passenger Car /Pickup 24
Office without Truck Access Single Unit Truck 42
Commercial / Retail with Separate Truck Access Passenger Car /Pickup 24
Commercial / Retail without Separate Truck Access WB -50 Truck 45
Industrial with Separate Truck Access Passenger Car /Pickup 24
Industrial without Separate Truck Access WB -50 Truck 45
Recreational without Watercraft Access or Camping Passenger Car /Pickup 24
Recreational with Watercraft Access or Camping Motor Home /Boat 50
Agricultural Field Access Single Unit Truck 42
Municipal and County Roads WB -50 Truck 45
TABLE 4-1 DESIGN VEHICLE AND TURNING RADIUS BY LAND USE
Note: "with Separate Truck Access" indicates truck prohibition from primary access.
Entrances into mixed use developments will be designed to accommodate the largest
design vehicle expected to use that entrance.
F -82
4. Modification of an Existing Entrance
When an existing street is re- developed and modification of an existing entrance
is required, the entrance surface shall be extended to the right -of -way line or the
extent of disturbance to the existing entrance.
Commercial Entrances
All commercial entrances shall be designed in accordance with the entrance design
diagrams Figures 4 -8 to 4 -15 to promote safe and efficient movement of vehicles in the
entrance and on state highways.
An access shall not be approved for parking areas that require backing maneuvers
within state highway right -of -way. All off - street parking areas must include on -site
maneuvering areas and aisles to permit vehicles to enter and exit the site in forward
drive without hesitation.
Entrance Medians: Entrance medians should be used when two or more lanes are
required for both the entering and the exiting movements at the entrance.
Entrance medians shall have a minimum width of 4 feet.
All curbing within the highway clear zone shall be in accordance with VDOT's
Road and Bridge Standards, or as approved by the District Administrator or
designee, and appropriate for the operational speeds of the facility.
Non - regulatory signs shall not be placed in the portion of an entrance median
located within the right -of -way, or within the highway clear zone, and shall not
restrict intersection sight distances.
An entrance median should not contain structures, signs, or landscaping which
restrict sight distance. The minimum size of a entrance median island is 100
square feet.
Entrance Throat: The entrance throat should be designed to facilitate the movement
of vehicles off the highway to prevent the queuing of vehicles on the traveled way.
The throat length is based on the traffic a development will generate, not the
characteristics of the abutting highway. The more traffic using the entrance, the
greater the number of ingress /egress lanes will be needed within the entrance, which
determines the length of the entrance throat.
Both sides of the entrance throat need to be protected.
F -83
The length of the entrance -side throat needs to equal the exiting throat. When
entering vehicles stop to turn left there must be sufficient queuing length to prevent
other entering vehicles from backing up on to the highway. Minimum connection
throats are provided in the table below.
Entrance throats apply to entrances to commercial uses, corner clearance establishes
the "Throat" of a minor street intersecting a major street.
Summary of E ntrance Throats
Number of Egress Lanes Minimum Throat Length
left, thru and right)Feet
1 30
2 75
3 200
4 300
TABLE 4 -2
Source: Transportation & Land Development 2 " Edition 2003, Koepke and Stover
To assure that entrances are designed to provide for safe and efficient movements, it is
necessary to pay attention to critical dimensions and design features listed below.
Radius of curved approach /exit of entrance.
Flare size of angled approach /exit of entrance.
Entrance Distance or spacing between entrances.
Corner Clearance measured from a major intersection.
Angle of entrance.
Sight distance length of roadway visible to the driver required for vehicles to
make safe movements.
Entrance location in relation to other traffic features such as intersections,
neighboring entrances, and median openings.
Entrance throat distance needed into site to transition vehicles to the internal
circulation system of the site.
Right turn lanes to separate through and turning traffic on roadways to facilitate
right turns into the entrance.
Entrance Pavement: The type and depth of the pavement shall be clearly indicated on
the plans and /or permit application. The pavement of commercial entrances, turn lanes
and tapers shall be of asphalt, concrete, or pavers that is of a construction comparable
to the pavement of the adjacent roadway.
Access Vertical Alignment: The vertical alignment of all access locations should be
designed to minimize vehicle bounce and prevent high- centering of vehicles with a
maximum clearance of 4 inches. The maximum grade for an entrance should be 8% for
all commercial entrances.