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<br />Feb. 8, 1983
<br />
<br />II
<br />
<br />BIKEWAYS
<br />
<br />IV, BIKEWAY DESI(~N TABLES
<br />
<br />The first step in thelevaluation of a propo~,~:l project
<br />is an analysis of the roa~ design and the volume of motor
<br />vehicles (ADT). The following tables provide the designer
<br />with an understanding o[his present situation and enables
<br />him to progress to deulrmine design options. Depending
<br />upon the review of th~ service area, the probability of
<br />project implementadon,I review of abutting section, and
<br />funding, the appropriat~ design level can be determined.
<br />In the tables: '~
<br /> - Road sections c_u~rrently rated "good" or "fair"
<br />will generally not be ~ligible for shoulder or off-road
<br />construction. ~
<br /> - If a suitable paralle~ road or off-road bikeway exists,
<br />funding from Mn/DOT w~ll be denied.
<br /> - Off-road design w[~] be considered if shoulder con-
<br />struction cannot enhand~ the road to "good" or "fair"
<br />status.
<br />
<br />V, DESIGN CRITERIA
<br /> A. D~:SIGN SPE£D
<br />
<br /> Curvature, superel4vation, gradient and width of
<br />trave]ed way are geomet~ features which affect the speed
<br />at which a bicyclist can travel safely a~d with comfort. IQ
<br />addition, factors such as ~raffic, the type of bicycle,
<br />ca] condition of the rider, wind, surface condition, also
<br />affect the speed the cy~:list will travel. Although speed
<br />of over 30 mph is attainable, the average cyclist travels
<br />at much lower speeds.
<br />
<br /> Speed bumps intent~ed to cause cyclists to slow down
<br />in advance of intersect/orB etc. shall not be used because
<br />they may cause a cyclist !to fall and result in injuries. The
<br />design speed is normally ~etermined by the speed of the
<br />highway or street. These! design speeds are generally ad.
<br />equate for cyclist's use.
<br />
<br /> For off-road bikeways, the design speed should be
<br />20 mph. For long down~ades, longer than 500 feet and
<br />steeper than 4 percent, a~design speed of 30 mph should
<br />be used at the downhill en~l.
<br />
<br />B. CURVATURE
<br />
<br /> On-road bikeways Will have curvature as dictated
<br />by the highway. Since the~e curves are designed to accom-
<br />modate motor vehicles, ihey are generally adequate for
<br />bicyclists.
<br />
<br /> For off-road bikeway, s, the minimum radius of cur-
<br />vature must be consisten~with the design speed of the
<br />facihty. The follo~ng design values are applicable where
<br />only standard cross-slope~.02 foot per foot) is provided:
<br />
<br />Design Speed Design Radius
<br />mph feet
<br />10 15
<br />15 35
<br />20 70
<br />25 90
<br />30 125
<br />
<br />Where more than standard cro~-dope is provided see
<br />Figure A for curve radii.
<br />
<br />C. SUPERELEVATION
<br />
<br /> As with curvature, supere[evation on shared roadway
<br />facilities the highway superelevation or shoulder slope w/Il
<br />govern and be more than adequate for cyclists.
<br />
<br /> However, with off-road bikeways, some superele-
<br />vation should be provided on all curves, .05 foot per foot
<br />should be used as the general design value and .02 foot per
<br />foot as the absolute minimum value (the minimum rate
<br />of cross slope required for drainage). In some cases, a
<br />rate of superelevadon greater than .05 foot per foot may
<br />be advantageous; however, pedal clearance must be con-
<br />sidered when increased super is used. A straight .02 foot
<br />per foot cross slope is recommended for tangent sections.
<br />
<br />D. GRADES
<br />
<br /> The grade which a bicycle can be expected to ne-
<br />gotiate is dependent upon the length of the grade, charac-
<br />teristics of the bicyclist (age, weight, condition, etc.),
<br />characteristics of the bicycle (type of cycle, gear ratios.
<br />weight, tires, etc.), wind velocity, air resistance and road
<br />surface. As all of these determinants are variable, it is
<br />not possible to specify definite design grades. Generally
<br />speaking, the amount of energy required to use a bicycle
<br />route will affect the usa.ce of the route and, thus, grades
<br />should be kept to a minimum.
<br />
<br /> The grade for on-road bikeways is generally adequate
<br />for cyclists, with little or no room for design change since
<br />it is a part of the road structure.
<br />
<br /> Desirably, a grade of 5% should not be longer than
<br />100 feet and a grade of 2% should not be longer than 500
<br />feet. Grades of 5% for over 300 feet and 2% for over 1.500
<br />feet should be avoided. Grades should be minimized even
<br />at the expense of having to provide added curvature or
<br />travel distance, within the practical limits for the site.
<br />The designer is offered some latitude in selecting profile
<br />grades for off-road bikeways but this is not the case for
<br />on-mad bikeways.
<br />
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