4.1
Purpose
(1) The Department has
developed the following design and construction standards and specifications
for application in Code decisions to protect the public health, safety, and
welfare; maintain smooth traffic flow; maintain highway right-of-way drainage;
and protect the functional level of public highways.
4.2
Use of Section Four
(1) If the issuing authority determines that
an application for access meets the requirements of Section Three, Section Four
shall be used to precisely locate, design and construct the access within the
criteria set forth in Section Three. When a local government is the issuing
authority and it has established by ordinance or resolution more stringent
design standards than required in this section, the local standards may govern
where applied by the local authority and is determined acceptable to the
Department. All construction materials, techniques and processes shall be in
conformance with the specifications on the permit, and shall not be
inconsistent with Department standard specifications for road construction. A
proposal for access may not presume a lower posted speed limit than currently
posted or request a lower speed limit in order to accommodate the access unless
specifically directed in writing by the Department.
(2) If an access application meets Section
Three criteria and is unable to comply with Section Four criteria, the access
permit should be denied unless a design waiver is authorized pursuant to
Section Four. When the access permit has been issued and later design
development does not meet Section Four, then the Notice to Proceed cannot be
issued unless a design waiver is approved.
(3) This section relies on general design
techniques. The use of more exact geometric engineering standards and methods
is permissible provided the design meets Code purposes, does not violate Code
standards, and is based upon desirable nationally accepted standards and is
determined acceptable to the Department.
(4) Speed, as used in this section, refers to
the posted legal speed limit at the access location at the time of permit
approval except as adjusted by 4.8(1)(e). A higher speed for access design
shall be used if the section of highway is presently being redesigned or
reconstructed to a higher speed or an approved access control plan requires a
higher speed. Where a traffic signal will be installed as part of the access
construction, the access design and the anticipated posted speed limit after
signal installation may be used for the overall access design at the discretion
of the Department.
(6) When
determining the distance between accesses, the point of tangency shall be used
where a radius is present, or the beginning of the curb cut. More complex
accesses including ramp connections shall be measured from the beginning of the
radii along the state roadway or between 2 points determined by the
Department.
4.3
Sight Distance
(1) Permits shall
not be issued that include any design element or allow any turning movements
where the sight distance is not adequate to allow the safe movement of a
motorist using or passing the access. The permittee shall maintain adequate,
unobstructed sight distance in both directions from the access. This sight
distance shall be the distance necessary according to the posted speed of the
highway using the tables below. Any potentially obstructing objects such as but
not limited to advertising signs, structures, trees, and bushes, shall be
designed, placed and maintained at a height not to interfere with the sight
distance needed by any vehicle using the access. Reconstruction of the
horizontal and vertical curvature along the roadway and side slopes adjacent to
the roadway may be necessary to increase sight distances to meet the
requirements of tables 4-1 and 4-2.
(2)
Sight Distance Along
Highway.
(a) Table 4 - 1 shall be used
to determine the required horizontal and vertical sight distance necessary as
measured from the vehicle traveling on the highway to the access. The design
sight distance figures shall be used unless a design waiver is issued in
accordance with section 4.12 . However, in no case shall the sight distance
used be less than the minimum sight distance set forth in table 4-1 and
adjusted for grade as required by table 4-4.
Table 4 - 1 Sight Distance Along Highway
Posted speed in MPH
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
65
|
70
|
Design sight distance (in feet)
|
150
|
200
|
250
|
325
|
400
|
475
|
550
|
650
|
725
|
850
|
Minimum sight distance (in feet)
|
150
|
200
|
225
|
275
|
325
|
400
|
450
|
525
|
550
|
625
|
(b)
For calculating table 4 - 1, sight distance at the proposed access location, a
height of 3.5 feet shall be used for the driver's eyes of a vehicle on the
highway approaching the access location. The driver's eyes shall be assumed to
be at the centerline of the inside lane (inside with respect to the curve) for
measurement purposes. A height of 4.25 feet shall be used for a vehicle assumed
to be on the centerline of the access five feet back from the edge of the
roadway.
(c) The lengths shown in
table 4-1 shall be adjusted for any grade of three percent or greater using the
figures set forth in table 4 - 4. Grade is the ratio of the change in elevation
to the length of slope. Multiply the length required in table 4-1 by the
appropriate factor in table 4-4.
(3)
Entering Sight Distance
(a) In addition to the sight distance
necessary in accordance with section 4-3(2), it is also necessary to provide
the entering vehicle adequate sight distance in order to enter or cross the
highway. Table 4-2 shall be used to establish the minimum sight distance
necessary for the entering vehicle. These lengths shall be adjusted for any
grade of three percent or greater using table 4-4. The vehicle used to
determine the entering sight distance necessary shall be selected from table
4-3.
(b) For calculating table 4-2
sight distance, a height of 3.5 feet shall be used for the driver's eyes at the
access location and a height of 4.25 feet for the oncoming vehicle. The
entering driver's eyes shall be assumed to be 10 feet back from the edge of the
roadway.
(c) If there is no median
or if the median is too narrow to safely store a left turning or crossing
vehicle, a 20 foot minimum is necessary for passenger cars, both directions
shall be considered from the access location. If the median can safely store
the turning or crossing vehicle, then the sight distance shall be calculated
assuming a two stop condition. The vehicle shall be assumed to stop once at the
outside edge of the outside lane and again within the median. Each one-way
roadway direction shall be considered separately.
Table 4 - 2: Entering Sight Distance (in
feet)
Vehicle expected to enter or cross highway as
determined from table 4-3
|
Posted Speed of Roadway in
MPH
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
65
|
70
|
Two Lane Roadway
|
Passenger Cars, Pickup Trucks
|
250
|
300
|
350
|
400
|
450
|
500
|
550
|
600
|
650
|
700
|
Single Unit Trucks Over 10,000 lb GVW
|
325
|
390
|
455
|
520
|
585
|
650
|
715
|
780
|
845
|
910
|
Multi-Unit Trucks
|
425
|
510
|
595
|
680
|
765
|
850
|
935
|
1020
|
1105
|
1190
|
Four Lane Roadway
|
Passenger Cars, Pickup Trucks
|
300
|
360
|
420
|
480
|
540
|
600
|
660
|
720
|
780
|
840
|
Single Unit Trucks Over 10,000 lb GVW
|
375
|
450
|
525
|
600
|
675
|
750
|
825
|
900
|
975
|
1050
|
Multi-Unit Trucks
|
500
|
600
|
700
|
800
|
900
|
1000
|
1100
|
1200
|
1300
|
1400
|
Six Lane Roadway
|
Passenger Cars, Pickup Trucks
|
325
|
390
|
455
|
520
|
585
|
650
|
715
|
780
|
845
|
910
|
Single Unit Trucks Over 10,000 lb GVW
|
425
|
510
|
595
|
680
|
765
|
850
|
935
|
1020
|
1105
|
1190
|
Multi-Unit Trucks
|
525
|
630
|
735
|
840
|
945
|
1050
|
1155
|
1260
|
1365
|
1470
|
Table 4 - 3: Design Vehicle Selection
Land Use(s) Served by Access
|
Design Vehicle(s) to be Used for Sight
Distance Calculations for table 4 - 2
|
Residential (a non-school bus route)
|
Passenger Cars, Pickup Trucks
|
If access is a part of any school bus route
regardless of land use
|
No less than Single Unit Trucks
|
Office
|
Single Unit Trucks
|
Recreational
|
Single Unit Trucks
|
Commercial/Retail
|
Multi-Unit Trucks*
|
Industrial
|
Multi-Unit Trucks*
|
Municipal Streets & County Roads
|
Multi-Unit Trucks*
|
Agricultural Field Approaches, < 1 per
day
|
Single Unit Trucks
|
*If less than 2 multi-unit truck trips per day
(average), use single-unit truck
|
Table 4 - 4: Stopping and Deceleration Adjustment
Factors for Highway Grade
3% to 4.9% Upgrade, Use 0.9
|
3% to 4.9% Downgrade, Use 1.2
|
5% to 7% Upgrade, Use 0.8
|
5% to 7% Downgrade, Use 1.35
|
4.4
Access Spacing
(1) When access is allowed in accordance with
Section Three of the Code, each access should be separated at a minimum by a
distance equal to the design sight distance values in table 4 - 1. When speed
change lanes are present, or will be needed in the future, it is desirable that
the accesses be separated by a sufficient distance so that the speed change
lanes including transition tapers do not overlap or an equivalent distance if
speed change lanes are not yet built. Access should not be permitted within an
auxiliary lane, taper or ramp.
4.5
Access Width
(1) Access width is the actual traveled
portion of the access as it extends away from the roadway. Access width for any
type access without curbs shall be measured exclusive of the radii or flares.
Width of an access with a curb return entrance and driveways with curb cuts,
shall be measured exclusive of the flared sections, transitions, curb and
gutter. The width of any non-traversable median is not counted as part of the
access width. In measuring access width, only the travel portion of the access
is measured.
(2) Sixteen to 30 feet
of width shall be used for any two-way access when the single unit vehicle peak
hour volume does not exceed five except as noted in subsection
4.5(3).
(3) Twenty-five to 40 feet
of width shall be provided for any two-way access when any one or more of the
following apply to the access:
(a) Peak hour
vehicle volume of the access exceeds five.
(b) Multi-unit vehicles are intended to use
the access.
(c) Single unit
vehicles in excess of 30 feet in length will use the access.
(d) Special vehicles using the access exceed
16 feet in width.
(4) A
one-way access shall have a width of 16 feet to 18 feet. If two one-way
approaches (one-way in, one-way out) are adjacent to each other, they shall be
divided by a non-traversable median of at least four feet but no more than 25
feet wide and treated as one access. The access median shall be signed and
clearly visible.
(5) When a public
street, road, highway or any access intended to become a public way intersects
with a state highway, the long term traffic projections and consideration of
the modal use of the public way shall be used to select an appropriate access
width, subject to the approval of the Department. It is recommended that no
two-way public roadway access in excess of 10 D.H.V. be less than 36 feet in
width at the intersection exclusive of the radii.
(6) Where a private access will have high
traffic volumes, the access may be designed with curb returns and at a width
and design sufficient to accommodate the traffic volumes as determined by the
issuing authority subject to approval of the Department.
4.6
Access Radii
(1) Except for curb cuts, accesses shall have
20 foot radii unless criteria below requires otherwise.
(2) The equivalent turning radii of the
access shall accommodate the turning radius of the largest vehicle using the
access on a daily basis. Where paved shoulders are present, the radius is
measured to the edge of the closest lane. Where roadway shoulders are not
present, field and residential accesses should have 25 foot radii.
(3) For any access where multi-unit vehicles,
or single unit vehicles exceeding 30 feet in length, are intended to use the
access on a daily basis, the radii of the access should be determined using the
minimum turning path for the larger vehicle. It is desirable to use equivalent
three-centered compound curves or spiral curves rather than simple radii when
designing for larger vehicles. The curves used should ensure safe turning
movements without encroachment onto other highway travel lanes.
(4) If the frequency of multi-unit vehicles
or single unit vehicles over 30 feet in length is such that two such vehicles
may be reasonably anticipated to use the access at the same time, one entering
and one exiting, radii should be adequate to accommodate both vehicles with no
turning conflicts and without undue slowing.
(5) Where curbs are present, a curb cut style
driveway will normally be required. Radius curb returns may be used when
determined to be necessary, are not inconsistent with existing or planned
conditions, and acceptable to the local authority. The issuing authority or
Department shall determine if a curb cut or radius curb returns are required in
accordance with existing or planned conditions.
(6) When a public street, road, or highway or
any access intended to become a public way intersects with a state highway, the
design criteria of the local government and the Department shall be used to
select appropriate radii, corner and intersection design, subject to approval
by the Department. The final design should not be less than the minimums
contained in the Code.
(7) Where
there are numerous accesses, such as along an established municipal street or
road, it may be desirable to reduce the radii in order to improve visual and
physical separation of accesses. Where feasible or required by the Code, access
should be combined or closed to reduce the frequency of accesses and increase
the spacing between accesses.
(8)
To minimize pedestrian conflict and total access width at the roadway edge,
radii shall not be constructed larger than required to accommodate the volume
and types of vehicles using the access on a regular basis.
(9) Where access channelization islands are
installed, a 70 foot radius may be required for the channel lane. Traffic
islands should be 100 square feet in size or larger. The minimum size without a
waiver is 50 square feet. All islands must have tapered offsets beginning at 6
feet at the approach nose and tapering to 3 feet, or as approved by the
Department, from the edge of the highway traveled way to face of
curb.
4.7
Access
Surfacing
(1) Surfacing material may
include approved grades of gravel, concrete pavement, and bituminous pavement.
Hard surfacing includes either concrete or bituminous pavements. Roadway and
access surfacing treatments shall conform to Department or local authority
adopted specifications which ever is greater.
(2) The access shall be surfaced upon
completion of earthwork construction and prior to being used. At locations
where new hard surface pavement is to abut existing pavement, the existing
pavement shall be saw cut and removed a minimum of one foot back from the
existing edge for bituminous, or until an acceptable existing cross slope is
achieved. A delay in installation of hot bituminous pavement due to seasonal
restrictions may be allowed provided adequate temporary gravel surfacing is
substituted.
(3) The access shall
be surfaced at least from the highway roadway to the right-of-way line. Any
access with greater than 5 AADT shall have a hard surface pavement for a
minimum distance of 4 feet from the traveled way. Any access with greater than
20 AADT shall have a hard surface pavement for a minimum distance of 20 feet
from the traveled way. Any access with greater than 100 AADT shall have a hard
surface pavement for a minimum distance of 50 feet from the traveled way. Any
access requiring a turn lane shall have a hard surface pavement for a minimum
distance of 50 feet from the traveled way.
(4) Surfacing material and depth shall be
specified and installed according to the Department's standard design
specifications and the conditions and future use of the access and the highway.
Aggregate base course Class 6 or equivalent may be permitted for individual
residential access or field entrances where conditions allow, and where curbs
are not required.
(5) Off roadway
surfacing improvements shall not be allowed within the highway right-of-way
unless approved by the Department and a concrete curb or other physical
separator such as a drainage ditch is constructed and maintained to limit
access movements to permitted locations.
(6) A two inch overlay of the entire width of
the roadway may be required when determined by the Department to be necessary.
The Department will look at the current condition of the roadway and the
additional impacts to surface quality and roadway strength given the access
impacts, where through lanes are redirected, where restripping is necessary,
where the centerline of the roadway is shifted, where it is necessary to reset
the high point in the roadway cross section that determines the direction of
surface drainage, or to allow for the regrade of the surface to meet surface
drainage requirements.
4.8
Speed Change Lanes
(1)
General Criteria for Speed Change
Lanes
(a) The warrants and elements for
the construction of speed change lanes is set forth in Section Three. When
speed change lanes are required, they shall be constructed in accordance with
this subsection and other applicable parts of Section Four.
(b) When public safety so requires due to
site specific conditions, such as sight distance, a turn lane may be required
even though the criteria in Section Three are not met.
(c) Where there are three or more through
lanes in the direction of travel, the Department shall not require a right turn
acceleration and or deceleration lane unless it is determined to be necessary
due to high traffic volumes or when a significant roadway capacity, operational
or geometric safety problem will exist. Each case shall be reviewed
independently and a decision made based upon site specific conditions. Strong
consideration shall be given to the opinion of the local municipality and their
concerns regarding the anticipated and desirable future cross section of the
highway.
(d) Where two accesses
have speed change lanes that overlap, or the ending points of the speed change
lanes have less than 300 feet or one-half their length of separation (whichever
is shorter) and a significant structure or topographical feature does not
preclude widening, a continuous auxiliary lane shall be established between the
accesses to improve roadway consistency, safety, and to maintain edge of
pavement continuity.
(e) If the
design of the access is within two different speed zones, the design of a speed
change lane shall be based upon the applicable speed limit. Generally, the
entering posted speed is used for the deceleration lane, and the posted speed
at the end of the acceleration lane is applicable.
(f) Where there are higher left turning
volumes, safety or traffic operations necessitate, a double left turn may be
required.
(g) A speed change lane
for acceleration and merging onto travel lanes should be parallel and
immediately adjacent to the traveled way for its entire acceleration and
transition taper length. Where the acceleration length is not parallel to the
traveled way, there shall be a parallel full width auxiliary lane based upon
posted speed. The parallel length should be no shorter than a standard
calculated merge distance.
(h) If
restrictive topography allows only one auxiliary lane, normally a left turn
deceleration lane is given first priority. Where a left turn is installed and
or the travel lanes redirected, an overlay of pavement may be required by
section 4.7.
Click to view
image
(2)
Necessary Components Determining
Speed Change Lane Length
(a) The
components of an auxiliary turn lane consists of transition taper, full width
auxiliary lane, and storage length. The use of these three components varies
according to the assigned access category and to some extent, site specific
conditions. Table 4 - 5 summarizes the components of speed change lanes when
such lanes are required by the category standards. Read the category
requirements and subsection 3.5 to determine if any speed change lanes are
required. Table 4 - 5 is provided to be used in conjunction with table 4 - 6.
Table 4 - 5: Components of Speed Change Lane
Length
access category
|
Left turn deceleration lane
|
Right turn deceleration lane
|
Acceleration lane
|
F-W
|
Design must meet federal interstate standards, and
no less then E-X
|
E-X
|
taper + decel.length+storage
|
taper + decel. length
|
accel.length + taper
|
R-A
|
* decel. length + storage
|
* decel. length
|
* accel. length
|
R-B
|
* decel. length + storage
|
* decel. length
|
* accel. length
|
NR-A
|
* decel. length + storage
|
* decel. length
|
* accel. length
|
NR-B
|
taper + storage
|
taper + storage
|
* accel. length
|
NR-B >40mph
|
* decel. length
|
* decel. length
|
* accel. length
|
NR-C
|
taper + storage
|
taper + storage
|
* accel. length
|
NR-C >40mph
|
* decel. length
|
* decel. length
|
* accel. length
|
F-R
|
taper + storage
|
taper + storage
|
* accel. length
|
F-R >40mph
|
* decel. length
|
* decel. length
|
* accel. length
|
* Taper length is included within stated accel. or
decel. length.
|
(b)
To determine the required acceleration, deceleration lane and transition taper
length in table 4-5, use the criteria provided in table 4 - 6.
Table 4 - 6: Design Criteria for Acceleration and
Deceleration Lanes
Posted Speed Limit in MPH
|
25
|
30
|
35
|
40
|
45
|
50
|
55
|
60
|
65
|
70
|
Deceleration Length in feet
|
180
|
250
|
310
|
370
|
435
|
500
|
600
|
700
|
800
|
900
|
Acceleration Length in feet
|
N/A
|
190
|
270
|
380
|
550
|
760
|
960
|
1170
|
1380
|
1590
|
Transition Taper Ratio
|
7.5:1
|
8:1
|
10:1
|
12:1
|
13.5:1
|
15:1
|
18.5:1
|
25:1
|
25:1
|
25:1
|
(c)
Deceleration lengths shown in table 4-6, shall be adjusted for any grade of
three percent or more using the factors shown in table 4-4. Acceleration
lengths shown in table 4-6, shall be adjusted for any grade of three percent or
more using the factors shown in table 4-7. Where only the transition taper and
storage length is provided, the length of the lane including transition taper
shall be adjusted for grade using tables 4-4 and 4-7.
(d) When physical or legal constraints
necessitate reducing part of the deceleration length, the transition taper
length will be reduced first, then the deceleration length. This minimum design
criterion shall be used without waiver approval only on highways posted below
45 MPH when, (1) the requirements of table 4 - 6 are not feasible, and (2) the
access category is not a F-W or E-X, or (3) the highway has in that section,
four or more intersections per mile per side, and there is heightened driver
expectancy of vehicle speed changes, turning movements and weaving movements
along that section of highway. If the above reduction criteria are not
sufficient for shortening of the length due to the constraint, then any
necessary additional shortening of the lane can only be done by the design
waiver procedure.
Table 4 - 7: Grade Adjustment Factors For Acceleration
Lanes
Posted Speed MPH
|
25 to 45
|
50
|
55
|
60
|
65
|
70
|
3 to 4.9% Upgrade
|
1.3
|
1.4
|
1.5
|
1.5
|
1.7
|
1.8
|
5 to 7% Upgrade
|
1.5
|
1.8
|
2.0
|
2.3
|
2.5
|
3.0
|
3 to 4.9% Downgrade
|
0.7
|
0.65
|
0.65
|
0.6
|
0.6
|
0.6
|
5 to 7% Downgrade
|
0.6
|
0.55
|
0.55
|
0.5
|
0.5
|
0.5
|
(e)
Where noted by table 4 - 5, or the auxiliary lane requirements of the category
description in Section Three, speed change lane storage lengths shall be
included in the design as provided in table 4-8.
Table 4 - 8: Storage Lengths
Turning Vehicles Per Peak Hour
|
below 30
|
30
|
60
|
100
|
200
|
300
|
Required Lane Length in Feet
|
25
|
40
|
50
|
100
|
200
|
300
|
(f)
Table 4-8 is based on automobile lengths. To allow for the impact of larger
trucks, buses and recreational vehicles, "passenger car equivalents" shall be
determined. Use a passenger car equivalent of 3 for each bus and all trucks and
combinations of 40 feet in length or longer. Use a passenger car equivalent of
2 for each vehicle or combination at or over 20 feet in length but less than 40
feet.
(3)
Speed
Change Lane Width
(a) Speed change
lanes shall normally be 12 feet wide exclusive of gutter pan or shoulder. If
existing through travel lanes are less than 12 feet wide and if local
government standards concur, an 11 foot width may be used. Where necessary, a
minimum of 10 feet of width is allowable on highways with a posted speed of
less than 45 MPH and less than 10 percent trucks. Speed change lanes should be
a minimum of 11 feet wide on highways with a posted speed above 40 MPH, or
where percentage of large trucks using the lane exceeds 9 percent.
(4)
Shoulder Width Along
Speed Change Lanes Where Curbs are not Present
(a) When necessary to redirect the traveled
way or install a speed change lane, a paved shoulder adjacent to the lane shall
be provided where no curb and gutter is present.
(b) Shoulders adjacent to the traveled way
should be a minimum of six feet in width but no less than the width of the
current shoulder. Shoulders adjacent to the traveled way should not be less
than 10 feet in width on any highway designated as part of the National Highway
System.
(c) Shoulders adjacent to a
speed change lane shall be four feet in width.
(5)
Taper Designs
(a) The length of the transition taper for
the auxiliary lane shall be determined according to the values given in table 4
- 6, which are the ratio of transition taper length to speed change lane width.
The length of a transition taper is calculated by multiplying the width of the
speed change lane by the ratio value associated with the posted speed in table
4 - 6. A 25 MPH zone and a 12 foot wide speed change lane at a 7.5:1 ratio,
requires a 90 foot transition taper. The beginning and ending point of all
tapers shall be rounded.
(b) It is
recommended that bay tapers be used (asymmetrical reverse curves) for
deceleration transition tapers and that straight transition tapers be avoided
at speeds above 40, and where a vertical cresting, or horizontal curve is
present, substituting an immediate bay taper and auxiliary lane striping to
reduce drifting of the through vehicles into the deceleration lane. Where
horizontal or crest vertical curves exist, the Department may require the
deceleration transition taper to begin with an immediate asymmetrical reverse
curve bay taper of 1/3L then 2/3L with the remaining required transition taper
length at full lane width.
(c)
Partial tangent transition tapers, symmetrical reverse curve tapers, or
asymmetrical reverse curve tapers may be used for transition taper design
provided a radius of at least 150 feet is used in curve calculations.
(d) Where it is necessary to establish a left
turn lane or median island, or otherwise redirect the vehicles on the traveled
way, redirect tapers required for redirecting through travel lanes shall be
installed according to table 4 - 9. If the use of table 4 - 9 would create a
horizontal curve design deficiency for the through movement, the horizontal
curve shall be corrected in addition to the use of redirect tapers. A redirect
taper should normally be a straight taper with the beginning and ending points
rounded.
Table 4 - 9: Redirect Tapers for Through
Lanes
Posted speed in MPH
|
30 or less
|
35
|
40
|
45
|
50
|
55
|
60
|
65
|
70
|
Straight Taper Ratio
|
15:1
|
20:1
|
30:1
|
45:1
|
50:1
|
55:1
|
60:1
|
65:1
|
70:1
|
(6)
Median Design for Turn Lane
Installation
(a) Where a single left
turn lane is necessary, a median area of 16 feet shall be provided. The median
area will normally consist of a 12 foot turn lane and a 4 foot painted
separator. Where a median area does not exist or where the painted median area
is less than 16 feet in width and a left turn lane is required, the roadway
shall be widened sufficiently in order to provide a median of at least 16 feet
in width to accommodate the left turn lane. If a barrier median is necessary,
the median area should consist of a 12 foot lane exclusive of gutter, and a
minimum 6 foot raised median divider. Existing raised or other non-traversable
medians shall not have new openings unless a study analyzing all related
traffic and safety issues is completed to the satisfaction of the Department
and the Department issues a written determination why the median opening is
acceptable.
(b) Where there is a
median of 16 feet or greater in width, the existing width may be used. Where
the existing median is a non-traversable barrier design, any new median
construction shall also be of similar barrier design unless otherwise
instructed by the Department. These design features may be modified at the
discretion of the Department where physical constraints, curbs, sidewalks,
structures, and lack of available right-of-way restricts
installation.
(c) Where it is
necessary to widen a highway for a median and public right-of-way is made
available, the highway should be widened equally on both sides in order to
maintain the existing highway centerline alignment.
4.9
Other Design
Elements
(1) When an access permit
requires the horizontal or vertical realignment of travel lanes, the design of
the roadway horizontal and vertical curves, superelevations, transitions, and
related specifications, should be those necessary to meet the posted speed or
advisory speed of the highway or the desirable overall design speed of the
existing highway, or current design standards, whichever is reasonable given
safety considerations, topography and costs. The design of the other elements
of the highway shall be no less than the current highway design unless
specifically directed by other sections of the Code.
(2) For all curb cuts, the vertical curve
from the traveled way into the access shall be the flattest curve that can be
obtained. To prevent the center or overhang drag of a vehicle, with some
allowance for vehicle load and bounce, crest vertical curves should not exceed
a four inch hump in a 10-foot chord and sag vertical curves should not exceed a
four inch depression in a 10-foot chord. For any access that is not a curb cut,
including streets and private access using curb returns, the first 20 feet
beyond the closest highway lane, including speed change lanes or the distance
to the side drain, whichever is greater, shall slope down and away from the
highway at a two percent grade to ensure proper drainage control. Exceptions
may be made where steep topography, such as a mountain, makes this requirement
very difficult to fulfill. The approved design must protect the highway from
drainage flows. Valley gutters are not recommended. Where super elevations are
present due to horizontal curves, drainage adjustments may be necessary at
Department approval.
(3) Within the
right-of-way, maximum grades shall be limited to ten percent for low volume
field and residential access. All other accesses shall be limited to a maximum
of eight percent grade. Lesser grades may be required for drainage control
purposes. Use of the right-of-way for access purposes should not preclude
future roadway use of the public rights-of-way. The length of the access within
the right-of-way should be minimized. Any access horizontal or vertical curve
should be minimized within the right-of-way so as not to interfere with the
future use, widening, reconstruction, or realignment of the highway within the
right-of-way.
(4) The horizontal
axis of an access to the highway shall be at a right angle to the centerline of
the highway and extend a minimum of 40 feet from the edge of the roadway or to
the right-of-way line, whichever is greater. An angle between 90 and 60 degrees
may be acceptable only if significant physical constraints require a skew angle
less than 90 degrees and is approved by the issuing authority and the
Department based upon site specific conditions. When horizontal curves are
present, the issuing authority or Department may require a different access
approach angle to improve entering sight distance.
(5) Access specifications shall ensure that
the access is designed and constructed in a manner that will encourage proper
use by the motorist. Access limited to right turns may be requested to have a
positive barrier such as a non-traversable median to prevent unauthorized turns
either on the roadway or using the access. Channelized driveway islands may be
required for turn restricted driveways when the driveway volume is predicted to
exceed 100 DHV, no restrictive center median is in place or programmed to be
constructed or it is likely that there will be frequent violations of the turn
restrictions. Channelized driveway islands are normally not required when the
driveway volume is lower and it is unlikely that there will be frequent
violations of the turn restrictions.
(6) An access that has a gate across it shall
be designed so that the longest vehicle using it can clear the roadway when the
gate is closed. If significant topographical features make this requirement
infeasible, providing a wide shoulder for temporary standing while the gate is
operated may be permitted or required.
(7) The access shall be designed to
facilitate the movement of vehicles from the highway to prevent the queuing of
vehicles on the roadway. An access shall not be approved for parking areas that
require backing maneuvers within state highway rights-of-way. All off-street
parking areas must include on-site maneuvering areas and aisles to permit user
vehicles to enter and exit the site in forward drive without hesitation other
than as directed by official traffic control devices. The issuing authority may
request the review of the parking lot layout and provide those terms and
conditions and those design requirements necessary to ensure the safe use of
the access.
(8) Fill slopes and cut
slopes shall be constructed either to (a) current Department minimum standards,
or (b) to the slope of the existing highway near the access, whichever is
determined appropriate by the Department and or the municipality if in an
incorporated area. It is desirable that all side slopes have a slope of 6:1 for
12 feet. The minimum side slope template shall provide a 4:1 slope for six
feet, and then not steeper than 3:1 unless physically restricted. Tighter
slopes may be permitted when proven necessary and approved by the appropriate
Department Region Transportation Director. Soil preparation including top soil,
seeding and mulching is required within the highway right-of-way on all
disturbed areas not surfaced, and, those areas beyond the highway that may
erode and send debris into the highway right-of-way. The Department or local
municipality will provide minimum seed mixes, types and rates of seeding and
preparation. The applicant may use an alternative mix and landscape plan if
approved by the Department or municipality.
(9) Access design shall provide for the safe
and convenient movement of all highway right-of-way users and modes of
transportation, including but not limited to pedestrians, bicyclists, transit
and the physically challenged. Sidewalks may be required where deemed
appropriate by the Department or when required by the local authority. Bike
paths and a local commitment to maintain the facility, may be included in the
access permit requirements upon request by the local authority.
(10) In the event it becomes necessary to
remove any right-of-way fence, the posts on either side of the entrance shall
be securely braced with an approved end post before the fence is cut to prevent
any slacking of the remaining fence. All right-of-way fence posts and wire
removed are Department property and shall be turned over to a representative of
the Department. Installation or removal of any right-of-way fence by the
permittee shall not be inconsistent with right-of-way fence law in section
35-46-111, C.R.S.
(11) Further details of access construction
and design, including pavement thickness and specifications, curb design and
specifications, roadway fill design and compaction, testing and inspection, and
other specific details, may be provided by the Department.
(12) Installation of any traffic control
device necessary for the safe and proper operation and control of the access
shall be required by the permit at the cost of the permittee. Arrangements to
share costs with other property owners and interests who will benefit from the
devices may be made by the permittee or local authority. Where the access may
warrant signalization in the future, phasing of the installation may be
required. All traffic control devices within the highway or other public
right-of-way or access that serve the general public shall conform to the
M.U.T.C.D.
(13) Physical separation
and delineation along a property frontage such as curb and gutter or fencing,
may be required where necessary to ensure that access will be limited to
permitted locations.
(14) Careful
consideration shall be given to the roadside clear zone. The permittee shall
provide adequate clear zone to the extent feasible. The access permit may
require that roadway hazards in the clear zone, such as fixed objects or steep
embankments, be removed, reconstructed or shielded by a proper barrier. In
urban areas with speeds of 40 MPH or less and vertical barrier curbs, a clear
zone of at least 18 inches minimum should be provided beyond the face of curb.
Where there is no curb in urban and rural areas and the speed is 40 MPH or
less, a minimum seven foot clear zone should be provided. At speeds of 45 MPH
or greater, the clear zone will vary from eight to 50 feet according to AADT,
travel speeds, roadway and roadside design. To the extent practicable, every
attempt will be made to adhere to standard clear zone practices and
guidelines.
(15) The permittee or
contractor shall not disturb any survey monuments found in state highway
right-of-way without specific Department authorization and direction. All costs
associated with the relocation or reestablishing of a survey marker will be
borne by the permittee. All survey procedures and minimum tolerances shall be
in conformance with the Department Survey Manual and the "Manual of Instruction
for the Survey of Public Lands of the United States" 1973, and section
38-53-101 et seq, C.R.S. Monuments
shall conform to Department standard M-629-1. The equipment used in referencing
or replacing monuments shall be able to produce the stated accuracies as
specified by the owner of the monument.
4.10
Emergency access
(1) An emergency access, when authorized in
Section Three, shall have a minimum width to serve oneway traffic and may be
less than 16 feet wide. The radii should be eliminated or reduced based upon
the assumption that fire equipment may encroach on other travel lanes. The
access profile can be individually designed without compromising drainage or
vertical curve minimums. Surfacing shall be chosen to minimize its visibility
while still providing sufficient strength. The emergency access shall have a
suitable barrier to eliminate non-emergency use and barrier design usually
based upon the standards of the local emergency services. The access shall not
be open for non-emergency uses and shall be maintained by the permittee as a
closed access except during emergencies. Any barrier shall not be in the state
highway right-of-way and will not be maintained by the Department. The access
shall remain closed at all times other than when in use for emergency purposes.
The access should be signed for emergency services only.
4.11
Drainage
(1) Each access shall be constructed in a
manner that shall not cause water to enter onto the roadway or shoulder, and
shall not interfere with the existing drainage system on the right-of-way or
any adopted municipal system and drainage plan. The highway drainage system is
for the protection of the state highway right-of-way, structures and
appurtenances. It is not designed or intended to serve the drainage
requirements of abutting or other properties beyond undeveloped historical
flow. Drainage to the state highway right-of-way shall not exceed the
undeveloped historical rate of flow.
(2) The permittee shall provide, at their own
expense, drainage structures for access which will become an integral part of
the existing drainage system. The type, design, and condition of these
structures shall meet the approval of the Department in unincorporated areas
and the municipality and the Department in incorporated areas. Drainage pipe
shall be a minimum of 18 inches in diameter or equivalent if not circular.
Flared end sections or other protective end treatments may be required for
culverts. Drainage structures under the access should extend beyond the access
radius to accommodate flattened side slopes.
(3) Where hydrological studies have been
completed, the drainage shall be designed to handle at least the 2 1/2 year
storm for an underground system and a five year storm for side drains but not
less than the existing drainage system. On larger systems and developments, the
effects of a 100 year flood event should be assessed. Where the specific
topography of the access site makes it likely that flooding in the highway and
overtopping of the roadway may occur, the drainage study shall consider and the
design reflect the 25 year flood for rural two lane highways, 50 year flood for
four lane highways, and 100 year flood in all urban areas. Cross drainage shall
be consistent with Department hydrology designs.
(4) The use of controlled flow detention
ponds shall be considered to control drainage flow from developed properties at
or below historical flow rates. All drainage appurtenances required for
detention and release shall be located and fully maintainable outside of the
highway right-of-way. When curb and gutter is required, the drainage ditch
should be eliminated by installing a storm sewer system. If a cross-pan is
necessary, it shall be at least 8 to 10 feet wide and 8 inches thick. If a
storm sewer system is available, it should be used, not a cross pan. All
proposed drainage controls and designs require Department approval. The areas
behind the curb and sidewalk shall have a down slope away from the roadway of
at least one percent.
4.12
Design Waiver Procedures
(1) If an applicant wishes to seek a waiver
from the design standards of the Code, a request must be submitted as an
attachment or addendum to a permit application form or provided with the
request for the Notice to Proceed. Department Form No. 112 shall be used. The
request for waiver shall state specific reasons why a waiver is necessary and
appropriate and include documentation to support such reasons. The request
shall address the waiver criteria of this subsection. Waivers cannot be issued
for procedural requirements. Separate waiver requests may be necessary where
several waivers are necessary and where the waivers may be approved in whole or
in part.
(2) The applicant may
supplement an application with a waiver request if the issuing authority
determines that sufficient time remains in the review period to consider the
waiver. If the issuing authority determines that it is in the public interest
to do so, the issuing authority may supplement a permit application with a
waiver.
(3) In consideration of a
waiver request, the issuing authority and Department shall determine if, (a)
absent approval of the waiver request, there is exceptional and undue hardship
on the applicant, and (b) a waiver would meet acceptable standards of practice
for engineering, operation and safety. A waiver may not be contrary to the
public interest, shall consider the orderly development plan of the local
government, shall consider the function of the highway, shall consider the
general design practices of the Department, and is subject to and limited by
the purposes of the Code as set forth in subsection 1.2.
(4) When a waiver is approved, the reasons
for granting the waiver and references to the specific standards of practice
shall be clearly stated in writing and included in the Department permit.
Restrictions on the use of the permit should be imposed as necessary to keep
potential safety problems to a minimum. By the terms and conditions of the
permit, the permittee may be required to improve, modify, eliminate, or correct
the condition giving rise to the waiver when it becomes evident that the reason
for the waiver no longer exists. If the waiver is approved and the remainder of
the application is in order, meets remaining Code criteria, a permit shall be
approved and the subsequent Notice to Proceed may be approved.
(5) If a waiver is granted to allow direct
highway access where the access proposal cannot meet regular access Code
standards, or when the property would be without reasonable access absent the
waiver, the access permit may contain specific terms and conditions providing
for its expiration at such time as the necessity for the waiver no longer
exists.
(6) If the waiver request
is denied, the issuing authority shall continue to process the permit
application in a standard manner and may issue a permit if it can be approved
without a waiver.
(7) The
recommendations and actions of the Department regarding the waiver shall be in
writing on form No. 112 with pertinent information attached and shall be
included as part of the permit application files. Waiver approval may only be
authorized by a licensed professional engineer. This may be the appropriate
Department Regional Transportation Director, or her or his designee, or Chief
Engineer. The Department may include in its action any special terms and
conditions that shall be imposed on the permit if approved.
(8) If the waiver request was not approved at
the Department's Regional level and if the applicant believes their request for
waiver was not given the consideration it deserves, or believes the decision
was not fair, the applicant may request a decision review by the Department's
Access Review Committee.