§ 152.31 DESIGN STANDARDS.

   (A)   Streets and roads.

      (1)   The design of all streets and roads within the town shall be in accordance with the accepted policies of the state’s Department of Transportation, Division of Highways, as taken or modified from the American Association of State Highway Officials’ (AASHO) manuals.

      (2)   The provision of street rights-of-way shall conform and meet the requirements of the thoroughfare plan for Gaston Urban Area as adopted by the City Council and the state’s Department of Transportation.

      (3)   The proposed street layout shall be coordinated with the existing street system of the surrounding area. Normally, the proposed streets should be the extension of existing streets if possible.

      (4)   The urban planning area shall consist of that area within the urban planning boundary as depicted on the mutually adopted Gaston Urban Area Thoroughfare Plan. The rural planning area shall be that area outside the urban planning boundary.

   (B)   Right-of-way widths. Right-of-way widths shall not be less than the following and shall apply except in those cases where right-of-way requirements have been specifically set out in the thoroughfare plan.

	Minimum Right-of-Way, Feet
Rural
Local road	60*
Major collector	100
Minor arterial	100
Minor collector	100
Principal arterial Freeways Other	350 200
Urban
Cul-de-sac	variable**
Local street	60*
Major thoroughfare other than freeway and expressway	90
Minor thoroughfare	70
*The desirable minimum right-of-way is 60 feet. If curb and gutter is provided, 50 feet of right-of-way is adequate on local residential streets. **The right-of-way dimension will depend on radius used for vehicular turn around. Distance from edge of pavement of turn around to right-of-way should not be less than distance from edge of pavement to right-of- way on street approaching turn-around.

 

      (1)   The subdivider will only be required to dedicate a maximum of 100 feet of right-of-way. In cases where over 100 feet of right-of-way is desired, the subdivider will be required only to reserve the amount in excess of 100 feet. In all cases in which right-of-way is sought for an access controlled facility, the subdivider will only be required to make a reservation.

      (2)   A partial width right-of-way, not less than 60 feet in width, may be dedicated when adjoining undeveloped property that is owned or controlled by the subdivider; provided, that the width of a partial dedication be such as to permit the installation of such facilities as may be necessary to serve abutting lots. When the said adjoining property is subdivided, the remainder of the full required right-of-way shall be dedicated.

   (C)   Street widths. Widths for street and road classifications other than local shall be as required by the thoroughfare plan. Width of local roads and streets shall be as follows.

      (1)   Local residential.

            (a)   Curb and gutter section: 26 feet, to face of curb.

            (b)   Shoulder section: 20 feet to edge of pavement, four-foot shoulders.

      (2)   Residential collector.

            (a)   Curb and gutter section: 34 feet, face to face of curb.

            (b)   Shoulder section: 20 feet to edge of pavement, six-foot shoulders.

   (D)   Geometric characteristics. The standards outlined below shall apply to all subdivision streets proposed for addition to the State Highway System or Municipal Street System. In cases where a subdivision is sought adjacent to a proposed thoroughfare corridor, the requirements of dedication and reservation discussed under right-of-way shall apply.

   (E)   Design speed. The design speeds for subdivision type streets shall be as follows.

	Desirable Level	(Minimum) Rolling Mountainous
Rural
Local roads including residential collectors and local residential	50	(50)*	(40)*	(30)*
Minor collector roads	60	(50)	(40)	(30)
Urban
Local streets	40	(40)**	(30)**	(20)**
Major thoroughfares other than freeway or expressway	60	(50)	(50)	(50)
Minor thoroughfares	60	(50)	(40)	(40)
*Based on projected annual average daily traffic of 400-750. In cases where road will serve a very limited area and small number of dwelling units, minimum design speeds can be reduced further. **Based on projected annual average daily traffic of 50-250.

 

   (F)   Maximum and minimum grades.

      (1)    The maximum grades in percent shall be as follows.

 

Design Speed	Level	Rolling	Mountainous
60	3	4	6
50	4	5	7
40	5	6	8
30		9	10
20			12

 

      (2)   A minimum grade for curbed streets normally should not be less than 0.5%, a grade of 0.35% may be allowed where there is a high type pavement accurately crowned and in areas where special drainage conditions may control.

      (3)   Grades for 100 feet each way from intersections should not exceed 5%.

      (4)   For streets and roads with projected annual average daily traffic less than 250, short grades less than 500 feet long may be 150% greater.

   (G)   Minimum sight distances. In the interest of public safety, no less than the minimum sight distance applicable shall be provided in every instance. Vertical curves that connect each change in grade shall be provided and calculated using the following parameters. (General practice calls for vertical curves to be multiples of 50 feet. Calculated lengths shall be rounded up in each case).

Design speed, mph	20	30	40	50	60
Stopping sight distance
Min. distance, feet	150	200	275	350	475
Des. distance, feet	150	200	300	450	650
Min. K* value for:
Min. crest curve	16	28	55	85	160
Des. crest curve	16	28	65	145	300
Min. SAG curve	24	35	55	75	105
Des. SAG curve	24	35	60	100	155

 

 

Passing Sight Distance
Min. passing distance, feet (two lane)	1,100	1,500	1,800	2,100
Min. K* value for crest vertical curve	365	686	985	1,340
Sight distance provided for stopped vehicles at intersections should be in accordance with, “A Policy on Geometric Design of Rural Highways”. *K is a coefficient by which the algebraic difference in grade may be multiplied to determine the length in feet of the vertical curve which will provide minimum sight distance.

 

   (H)   Maximum degree of curve and maximum superelevation. The following table shows the maximum degree of curve and related maximum superelevation for design speeds. The maximum rate of roadway superelevation (e) for rural roads with no curb and gutter is .08. The maximum rate of superelevation for urban streets with curb and gutter is .06 with .04 being desirable.

Design Speed MPH	Maximum e*	Minimum Radius (Rounded) Feet	Maximum Degree of Curve (Rounded) Degrees
20	.04	125	45.0
30	.04	300	19.0
40	.04	560	10.0
50	.04	925	6.0
60	.04	1,410	4.0
20	.06	115	50.0
30	.06	275	21.0
40	.06	510	11.5
50	.06	630	7.0
60	.06	1,260	4.5
20	.08	110	53.5
30	.08	250	23.0
40	.08	460	12.5
50	.06	760	7.5
60	.08	1,140	5.0
*e = rate of roadway superelevation, foot per foot

 

   (I)   Intersections.

      (1)   Streets shall be laid out so as to intersect as nearly as possible at right angles, and no street should intersect any other street at an angle less than 60 degrees.

      (2)   Property lines at intersections should be set so that the distance from the edge of pavement, of the street turnout, to the property line will be at least as great as the distance from the edge of pavement to the property line along the intersecting streets. This property line can be established as a radius or as a sight triangle. Greater offsets from the edge of pavement to the property lines will be required, if necessary, to provide sight distance for the stopped vehicle on the side street.

      (3)   Off-set intersections are to be avoided unless exception is granted by the Division of Highways for intersections involving the State Highway System, or the Planning Board for intersections involving only the municipal street system. Intersections which cannot be aligned should be separated by a minimum length of 200 feet between survey centerlines.

   (J)   Cul-de-sacs. Cul-de-sacs, unless exception is granted by the local planning board, shall not be more than 500 feet in length. The distance from the edge of pavement on the vehicular turnaround to the right-of-way line should not be less than the distance from the edge of pavement to right-of-way line on the street approaching the turnaround. Cul-de-sacs should not be used to avoid connection with an existing street or to avoid the extension of an important street.

   (K)   Alleys.

      (1)   Alleys shall be required to serve lots used for commercial and industrial purposes except that this requirement may be waived where other definite and assured provision is made for service access. Alleys shall not be provided in residential subdivisions unless necessitated by unusual circumstances.

      (2)   The width of an alley shall be at least 20 feet.

      (3)   Dead-end alleys shall be avoided where possible, but if unavoidable, shall be provided with adequate turnaround facilities at the dead-end as may be approved by the Planning Board.

      (4)   Sharp changes in alignment and grade shall be avoided.

(Prior Code, § 9-3022) (Ord. passed - -)