2 Colo. Code Regs. § 601-1-4

Current through Register Vol. 47, No. 20, October 25, 2024

Section 2 CCR 601-1-4 - Design Standards and Specifications

4.1Purpose

(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.

4.2Use 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.

4.3Sight 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

4.4Access 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.

4.5Access 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.

4.6Access 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.

4.7Access 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.

4.8Speed 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.

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(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.

4.9Other 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.

4.10Emergency 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.

4.11Drainage

(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.

4.12Design 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.

2 CCR 601-1-4