David Harrell, P.E.
|October 25, 2002|
CITY OF KNOXVILLE, TENNESSEE
DEPARTMENT OF ENGINEERING
Comments on Draft Guidelines on Public Rights-of-Way
SECTION 1102.2.2 Alterations. It is noted that alterations must not be fully compliant “where compliance is technically infeasible”. We find the statement to be too vague and believe it needs further clarification. The examples of technical infeasibility given in the “Discussion of Provisions” are extreme cases. For example, would adding a left turn signal to a signalized intersection that has a pedestrian signal system require making the pedestrian signal system fully accessible? If so, this could potentially turn a $400 upgrade into a $10,000 upgrade. We would consider this just as technically infeasible as “altering a load-bearing member of a structural frame”. While technically this could be done, the cost to make the area within the alteration fully compliant compared to the cost of the alteration itself would make the project no longer viable.
SECTION 1104.3.2 Detectable Warnings. We concur with the advisory committee’s comments on using detectable warnings on only those ramps that are the least distinguishable. While the revised specifications are an improvement we believe the truncated domes to be hazardous for elderly pedestrians and will still cause difficulties in maneuvering for wheelchairs.
SECTION 1104.3.3 Surfaces. When altering an existing facility such as adding a curb ramp where none exists, it is not always possible to locate the ramp to avoid manhole covers for utilities. While the elevation of these covers can be adjusted to match the slope and elevation of the ramp, it is impractical to have these manholes relocated. We would expect this situation to fall under the “technically infeasible” category.
SECTION 1104.3.6 Counter Slopes. Integral curb and gutter sections are typically slip-formed and typically have a cross-slope of 1:12. From a construction stand-point it is impractical to change the cross-slope through the curb ramp to 1:20. Most sidewalk widths are seven feet or less and are unable to have a 48”x 48” landing area at the top of a ramp which would require the curb ramp to be a parallel ramp. A parallel ramp has a maximum cross-slope of 1:48 making the transition from curb ramp to gutter 10%, which is less than the 11% recommended by the advisory committee.
SECTION 1105.2.2 Cross Slope. With terrain such that is typical in East Tennessee, profile grades of 9 or 10 percent are very common. This requirement would be extremely difficult, it not impossible, to implement for roads having grades of this magnitude. In order to make an intersection design work for a road of this type, the profile grade must be changed by 7 or 8 percent along a vertical curve that maintains the design speed of the road. Typically, the cross-slope of the intersecting street is often sloped as much as 4 percent to minimize the required change in profile grade of the through street.
SECTION 1105.4 Medians and Pedestrian Refuge Islands. The cut through concept is a good idea to provide access for pedestrian access but the need for pedestrian storage needs to be considered as well, e.g., when crossing pedestrians to the refuge island on one phase and then the remainder of the crossing under another phase. The situation could arise where several pedestrians would be crossing but not enough space is provided in the island crossing area and would leave some of the pedestrians in the roadway until the next pedestrian crossing phase.
SECTION 1105.7 Turn Lanes at Intersections. Most right-turn slip lanes have no signalized control other than a yield sign. It would not be practical to locate a pedestrian signal system at these locations as the slip lanes are not signalized. Signalizing the slip lane to enable the use of a pedestrian signal system would effectively remove the reason for providing the slip lane.
SECTION 1102.8 and 1106 Accessible Pedestrian Signal Systems. Is the requirement to install these devices at all existing signalized intersections that currently provide pedestrian signal systems or at only that intersection that will be constructed and/or upgraded. If the Board is advocating that all the pedestrian signal systems be upgraded then there needs to be some consideration to phasing in a program over time to help defer the cost of these upgrades. The cost could exceed $20,000 per intersection for the accessible pedestrian signal system at complex signalized intersections and could be much higher if the relocation of existing signal poles or the addition of pedestrian signal poles is required. Considerations should take for the cost of initial installation and the need for additional maintenance personnel to maintain this type of facility to insure proper operation.
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