A. General Provisions:
1. Compliance With Local And State Regulations:
a. Local Plan: Streets shall be planned and arranged to conform to the transportation policies and traffic map contained in the official county policy plan. For streets not shown on the county plan or map, the arrangement shall provide for appropriate extensions of existing streets and anticipated future development of adjacent areas. The county highway engineer and township road commissioner shall be consulted as to the appropriateness of any extensions that affect their jurisdictions.
b. State And Federal Guidelines: It is intended that the streets and roadways covered by this section be in substantial conformance with the Grundy County highway access regulation ordinance and the Illinois department of transportation standards and criteria and the guidelines contained in the American Association Of State Highway And Transportation Officials publication "A Policy On Geometric Design Of Highways And Streets". Variations of specific requirements of this section may be required or allowed to provide design flexibility tailored to particular situations, so long as such variations remain within the intended requirement limits and guidelines.
2. Residential Streets: Residential streets shall be arranged so as to discourage through traffic and provide for maximum privacy.
3. Design Associated With Speed Limit: The street requirements provided in this section are based on a design speed of forty (40) miles per hour for collector streets, thirty (30) miles per hour for subcollector and rural lanes, and twenty five (25) miles per hour for access streets and cul-de-sacs. When allowable design speeds are greater than these values, streets shall be designed in accordance with appropriate standards and criteria of the Illinois department of transportation, bureau of local roads and streets. Street design based on speeds less than those noted above may be required (or allowed) if warranted by development, topographic conditions, or the advice of the county highway engineer or township road commissioner.
4. Standards Applicable To Certain Types Of Streets: The design requirements indicated in this section are for streets and roadways within and adjacent to residential and nonresidential developments and subdivisions intended to serve local access and traffic collection needs. Roadways intended primarily to serve intracounty travel and provide only limited access to abutting lands (arterial and major collector roads) shall be designed in accordance with Illinois department of transportation procedures, standards, and criteria.
B. Street Hierarchy:
1. Streets shall be classified in a street hierarchy system with design tailored to function accordingly. The street hierarchy system shall be defined by road function and average daily traffic (ADT), calculated by trip generation rates prepared by the Institute Of Transportation Engineers. Trip generation rates from other sources may be used if the applicant demonstrates that these sources better reflect local conditions.
2. Each residential street shall be classified and designed for its entire length to meet the standards for one of the street types defined in section 8-17-1-4, figures 1 through 3 of this title. The applicant shall demonstrate to the county's satisfaction that the distribution of traffic to the proposed street system will not exceed the ADT guidelines indicated in section 8-17-1-1 of this title for any proposed street type. Anticipated future developed areas shall be taken into account in determining traffic volumes.
3. Nonresidential development and subdivision streets shall be classified and designed in accordance with the uses served and traffic types and volumes to be handled. Adequate allowance shall be made for generated truck traffic. The design of such streets shall be governed by applicable Illinois department of transportation procedures, standards, and criteria.
C. Pavement Width:
1. Pavement width for each street classification shall be determined by moving traffic, parking, and curbing requirements that are based on the form and intensity of development.
2. Intensity of residential development shall be based on lot frontage as follows in table 8-6-3-4, "Intensity Of Development", of this section:
Lot Frontage (In Feet) | Intensity |
More than 150 | Low |
80 to 150 | Medium |
Less than 80 | High |
3. Pavement width shall also consider possible limitations imposed by sight distance, climate, terrain, and maintenance needs. In order to minimize street costs, the minimum width assuring satisfaction of needs shall be selected.
4. Pavement widths required for each street classification are shown in section 8-17-1-2 of this title.
5. At medium development intensity, with lot frontage greater than one hundred fifteen feet (115'), the pavement width may be reduced (subject to county approval) to that required for low intensity development when front yard setbacks exceed sixty feet (60') and it can be demonstrated that sufficient off street parking will exist.
6. At intersections with significant left turn traffic, the pavement width shall be widened sufficiently to allow for a separate left turn lane. Minimum width of a left turn lane shall be ten feet (10').
D. Pavement Edges:
1. Curbing:
(1) For drainage control;
(2) To stabilize pavement edges;
(3) To delineate parking areas;
(4) At intersections;
(5) At corners; and
(6) At tight radii.
b. Where curbing is not required, some type of edge definition and stabilization shall be furnished for safety reasons and to prevent pavement deterioration.
c. At medium development intensity, the curbing requirement may be waived where front yard setbacks exceed sixty feet (60') and it can be demonstrated that sufficient off street parking will exist.
d. Flexibility regarding curb type shall be permitted as long as the curb type accommodates the system of drainage proposed. Typically, curbing shall be B6.12 or M3.12 curb and gutter depending on roadway type and site development conditions.
e. Depressed curb sections shall be installed where necessary to provide a ramp for bicycles and/or wheelchairs as required by state law.
f. Curbing shall be constructed according to the specifications included in this section.
2. Shoulders And Drainage Swales:
a. Shoulders and drainage swales shall be provided rather than curbs when:
(1) Shoulders are specified by other Illinois DOT or Grundy County highway standards.
(2) Soil or topography makes the use of shoulders and drainage swales preferable.
(3) It is in the best interest of the county to maintain its rural character by using shoulders and drainage swales instead of curbs.
d. Shoulders shall consist of compacted aggregate and earth material and shall be constructed according to the specifications included in this section.
E. Sidewalks And Pathways:
1. Sidewalks shall be provided, depending on road classification and intensity of development, in accordance with the requirements indicated in sections 8-17-1-2 and 8-17-1-4, figures 1 through 4 of this title. Sidewalks may also be required in proximity to pedestrian generators, to continue a walk on an existing street, to link pedestrian origin and destination areas, or to serve probable future development as indicated in applicable master plans.
2. In conventional subdivisions or development projects, sidewalks shall be placed in the right of way, parallel to the street, unless an exception has been permitted to:
a. Preserve topographical or natural features;
b. Provide visual interest; or
c. Unless the applicant shows that an alternative pedestrian system provides safe and convenient circulation.
3. Pathways are intended for bicycle traffic, as well as pedestrians, and may be required when:
a. Topography and/or site conditions make the use of pathways preferable;
b. It is in the best interest of the community to preserve its rural character by using pathways instead of sidewalks; or
c. Significant bicycle traffic is anticipated and it is desirable to keep such traffic off the roadway.
4. In planned residential or mixed use developments, sidewalks or pathways may be located away from the road system to link dwelling units with other dwelling units, the street, and on site activity centers such as shopping areas and school/recreational areas. They may also be required to be parallel to the street for safety and other reasons.
5. Pedestrianway easements (10 foot minimum width) and pavements may be required through the center of blocks more than six hundred feet (600') long to provide circulation or access to schools, playgrounds, shopping areas, or other community facilities.
6. Sidewalks shall typically be four feet (4') wide. Wider sidewalks may be necessary near pedestrian generators and employment centers. Sidewalks shall be at least six feet (6') wide where they abut curbs or pavements and are subject to vehicle overhang.
7. Pathways shall typically measure six feet (6') in width. Where significant two-way bicycle traffic is expected, an eight foot (8') width shall be required.
8. Sidewalks and pathways shall be constructed according to the specifications included in this section.
F. Bikeways:
1. Separate bicycle paths shall be required:
a. If such paths have been specified as part of the county's comprehensive plan; or
b. If such paths are necessary for pedestrian and bicycle traffic circulation within a planned residential or mixed use development.
2. Bicycle lanes, where required, shall be placed in the outside lane of a roadway, adjacent to the curb or shoulder. When on street parking is permitted, the bicycle lane shall be between the parking lane and the outer lane of moving vehicles. Lanes shall be delineated with markings, preferably striping. Raised reflectors or curbs shall not be used.
3. Bikeways shall be constructed according to the specifications included in this section and also conform to the easement provisions included in subsection 8-6-3-9B of this chapter.
G. Relationship Of Street, Utility, And Shade Tree Locations:
1. Sewer and water utilities shall generally be located within the right of way on both sides of and parallel to the street. Such utilities may also be located in easements adjacent to the right of way, depending on development and site conditions.
2. Underground electric, telephone, television, and other communication lines shall preferably be located within utility easements rather than within street rights of way. Poles for overhead utilities shall be located along street rights of way within two feet (2') of the property/right of way boundary line.
3. Trees along streets with curb and gutter edges and without parkway drainage swales shall be located within the street right of way. Trees along streets with drainage swales shall be placed outside of the street right of way (within 20 feet of said right of way) unless the street parkway is wide enough to avoid interferences between swales and trees. Refer to chapter 9, "Landscaping And Tree Protection", of this title, for additional tree location requirements.
H. Right Of Way:
1. The right of way shall be measured from lot line to lot line and shall be sufficiently wide to contain the required travel pavement, curbs or shoulders, sidewalks, drainage swales, utilities, and shade trees. Right of way widths shall be increased if necessary to accommodate major drainage swales, but swales may be partially located on easements adjacent to the right of way depending on development and site conditions. Typical right of way requirements are shown in sections 8-17-1-2 and 8-17-1-4, figures 1 through 4 of this title.
2. The right of way width of a new street that is a continuation of an existing street shall be continued at a width no less than that of the existing street.
3. The right of way shall reflect future development and traffic conditions anticipated by the county.
I. Cul-De-Sacs:
1. Maximum cul-de-sac lengths shall be a function of the type and density of development served. Rather than requiring a maximum length for all situations, cul-de-sacs shall be classified by traffic volumes (ADT) into the following two (2) street categories:
a. Residential access streets with a maximum ADT of two hundred fifty (250) and no length limit.
b. Subcollector with a maximum ADT of five hundred (500) and length limit of one thousand feet (1,000').
2. A length variance for a subcollector street will be considered if the cul-de-sac has a paved emergency access connection to an adjacent collector or higher category street.
3. Turnarounds shall typically be of a circular type with a minimum pavement radius of fifty feet (50'). Subject to specific county highway commissioner approval, turnarounds may be provided with a landscaped island. In such cases, minimum pavement width shall be twenty two feet (22').
J. Sight Distance:
1. Sight distances along roadways and at intersections shall be based on the design speed of the roadways.
2. Minimum stopping sight distance along any type of local street other than a collector shall be two hundred feet (200'). The minimum requirement along a collector street shall be three hundred twenty five feet (325').
3. Design for passing sight distance is seldom applicable on local streets and has not been used as a criterion in establishing the standards indicated in this section. If vehicle passing opportunities are considered necessary or desirable, the horizontal and vertical curve standards shall be adjusted to provide the passing sight distance required for the design speed established.
4. Minimum corner sight distance at intersections of local streets other than collectors shall be three hundred ten feet (310'). At a collector street intersection, the minimum requirement shall be four hundred fifteen feet (415'). Corner sight distance shall be measured from a point on the lower category street at least twenty feet (20') from the edge of the higher category street pavement.
5. Corner sight distance at the intersection of a local street with an arterial or major collector road shall be based on the design speed of said road. Fifty (50) miles per hour requires five hundred fifteen feet (515'), and sixty (60) miles per hour requires six hundred fifty feet (650').
6. To maintain visibility at intersections, sight triangle easements shall be provided at street corners.
a. These easements shall consist of the area within the triangle defined by the following lengths along the street right of way lines, measured from the intersection of said lines. The noted length for the no stop control condition is based on a thirty (30) mile per hour design speed for both streets. If the design speed for either street exceeds thirty (30) miles per hour, the sight triangle lengths shall be adjusted accordingly.
(1) Forty feet by forty feet (40' x 40') where stop control is provided.
(2) Ninety feet by ninety feet (90' x 90') where stop control is not provided.
b. Landscaping, structures, or other accessory uses shall comply with the provisions of section 8-2-3-16, "Vision Clearance For Corner Lots", of this title. A public right of entry shall be reserved for the purpose of removing any object or material that obstructs the clear sight.
c. Existing ground, vegetation, trees, and structures within this easement that would create a traffic hazard by limiting visibility shall be removed to the extent necessary to provide adequate visibility.
K. Grades And Vertical Curves:
1. Minimum street grade permitted for streets with curb and gutter shall be 0.5 percent. Where topographical conditions permit, grades in excess of 0.5 percent shall be used.
2. Maximum street grade shall vary by road hierarchy, with flatter grades required for roads with higher ADTs, in accordance with the requirements shown in section 8-17-1-3 of this title.
3. Intersections shall be designed with a flat grade wherever practical. Maximum grade within fifty feet (50') of intersections shall be as indicated in section 8-17-1-3 of this title.
4. Minimum length or crest and sag vertical curves shall be based on providing an adequate stopping site distance and shall be as shown in section 8-17-1-3 of this title.
L. Intersection And Roadway Geometrics:
1. Street intersections shall be as nearly at right angles as possible. In no case shall an intersection be at less than seventy five degrees (75°).
2. New intersections along one side of an existing street shall, if possible, coincide with any existing intersections on the opposite side of each street. Use of "T" intersections in subdivisions shall be encouraged. To avoid corner cutting when inadequate offsets exist between adjacent intersections, offsets shall measure at least one hundred seventy five (175) to two hundred feet (200') between centerlines.
3. Intersections shall be rounded at the surface edge (curb line), with the street having the highest radius requirement as shown in section 8-17-1-3 of this title, determining the minimum standard for all surface edges (curb lines).
4. Intersections with roads under the jurisdiction of an agency other than the county or local township shall be as specifically required by the subject agency.
5. Minimum requirements for centerline radius, tangent length between reverse curves, and edge radii shall be as shown in section 8-17-1-3 of this title.
M. Pavements:
1. Cross Section Slopes:
a. Pavement cross slope (crown) must be adequate to provide proper drainage. Bituminous pavement cross slopes shall be three- sixteenths inch (3/16") to three-eighths inch (3/8") per foot. Aggregate pavement cross slopes shall be one-fourth inch (1/4") to one-half inch (1/2") per foot.
b. Bituminous shoulder cross slopes shall be one-fourth inch (1/4") to one-half inch (1/2") per foot. Gravel shoulders shall be one-half inch (1/2") to three-fourths inch (3/4") per foot, and turf shoulders shall be three-fourths inch (3/4") to one inch (1") per foot.
c. At super elevated pavement sections, shoulder cross slopes shall be adjusted so that the algebraic difference between the pavement and shoulder slopes does not exceed eight percent (8%).
d. Front slopes of drainage swales shall not exceed three to one (3:1). Back slopes shall not exceed two to one (2:1). Back slopes more than four feet (4') high shall not exceed three to one (3:1).
e. Pavement superelevation is typically not used on local streets but, depending on conditions, may be required on collector streets. The rate of superelevation shall not exceed 0.08 foot per foot for rural conditions and 0.04 foot per foot for urban conditions.
2. Thickness And Materials:
a. Local streets covered by this chapter shall typically consist of bituminous concrete surface and binder courses, an aggregate base course, and a geotextile fabric placed on a suitable nonorganic subgrade.
b. Required pavement thickness shall be a function of traffic volumes anticipated, pavement materials used, and subgrade support available.
c. Pavement thickness design procedures and criteria shall be in accordance with the Illinois department of transportation publication "Structural Design Of Flexible Pavement".
d. Residential collector streets shall have a structural number of 3.0 or greater. The minimum structural number for all other local residential streets shall be 2.5. Streets intended for commercial or industrial development shall have a structural number of 3.0 or greater. These minimum requirements are based on a subgrade IBR value of 3.0. If this subgrade strength is not available, the pavement structure section shall be increased in accordance with IDOT design procedures.
e. Street pavements shall be constructed according to the specifications included in this chapter.
3. Typical Street Sections: Section 8-17-1-4, figures 1 through 4 of this title graphically display the various requirements indicated in this section. The street sections shown are intended to meet typical conditions and shall be required unless revisions are approved by the county. Such changes or variations will be allowed or required if, by reasonable and current engineering practices and standards, they are determined necessary to resolve specific traffic or site conditions.
N. Driveways:
1. Local access driveway connections to public streets shall typically be constructed in accordance with section 8-17-1-5 of this title.
2. Revisions to the requirements indicated in section 8-17-1-5 of this title, may be necessary to accommodate specific roadway, site or traffic conditions (see subsection M3 of this section).
O. Signs And Markings:
1. Traffic control signs and pavement markings shall be provided and installed in conformance with the principles and standards contained in the Illinois department of transportation publication "Manual On Uniform Traffic Control Devices" (MUTCD).
2. The locations and detailed requirements of regulatory and warning signs and pavement markings shall be as required by the county highway department.
3. Pavement centerlines shall be provided on streets with an ADT greater than five hundred (500) vehicles. Pavement edge lines shall be provided on streets with shoulders when the ADT exceeds five hundred (500) vehicles. Centerlines and edge lines shall also be provided in other situations when specifically required by the county.
4. Street name signs shall be installed at all street intersections. Placement, size and materials shall be in accordance with IDOT and MUTCD requirements. At four-way intersections, two (2) sign installations shall be provided. These signs shall be placed on diagonal corners so that they will be on the near left hand and far right hand sides of the intersection for vehicles on the street with the higher traffic volume.
5. Information signs in planned residential or mixed use developments shall be placed so as to avoid street sight distance and other traffic safety problems. Such signs shall also follow a design theme that is related and complementary to other elements of the overall site design. Placement, size, and appearance of information signs shall be subject to approval of the county.
6. Traffic control signs along public roadways shall be installed by the governing local agency (township or county highway department). Material and installation costs shall be paid for by the developer.
P. Street Lighting:
1. Streetlights typically shall be provided at all street intersections, at commercial/industrial driveways, at residential off street parking access drives, and at a spacing not to exceed six hundred feet (600') between intersections. Streetlights shall also be provided at curves where specifically required by the county.
2. Continuous lighting may be required along commercial/industrial land use streets and along collector streets within or adjacent to high and medium intensity developments. The need for continuous lighting shall depend on the intensity of land use, volume of vehicle traffic, and amount of pedestrian traffic.
3. The publication "American National Standard Practice For Roadway Lighting" shall be used as a guide in the design of street lighting systems. Illumination levels and uniformity ratios should be as recommended in that publication.
4. Streetlights shall typically consist of a sharp cutoff type luminaire, with a four (4) to six foot (6') bracket arm mounted on a concrete or steel standard (pole). Maximum mounting height within residential areas shall be thirty feet (30'). Specific luminaire and standard provided shall be as approved by the county.
5. Streetlights shall be provided and installed according to county specifications.
6. The owner, subdivider, and owners of each subdivision required by this section to have a street lighting system shall be required to establish a subdivision or homeowners' association to maintain the system. It shall be responsible for payment of the repair, replacement, maintenance, and energy costs generated by the street lighting system once it is provided by the owner or subdivider. The association shall be responsible for payment directly to the provider of repair, replacement, maintenance, or energy services. The association shall keep the street lighting system in good repair and shall repair or replace nonoperating fixtures or other portions of the system within thirty (30) days of the time they become nonoperational. (Ord. 10-001, 1-12-2010)