Three alternative roadway sections are being considered for the project:

1. 78’ R/W – This is the current design, and is based on the existing CAMPO Thoroughfare Plan. This section consists of four 11’ lanes with additional turn lanes at major intersections, a 4’ concrete median, and curb and gutter and sidewalks both sides.
2. Other considerations for this section are:
   1. Add 4’ bike lanes inside curb and gutter. This could add 8’ to the required R/W.
   2. Add 10’ bike lane outside of curb and gutter one side instead of sidewalk. This could add 10’ to the required R/W.
3. 100’ R/W - This section consists of five 12’ lanes with a 4’ bike lane, curb and gutter, and sidewalks both sides.
4. Other considerations for this section are:
   1. Increase width of center lane as required to allow reversible lane signalization. The 100’ R/W would accommodate a center lane of up to 18’ width.
5. 138’ R/W - This section consists of six 12’ lanes with a 30’ raised median, with a 4’ bike lane, curb and gutter, and sidewalks both sides.
6. Other considerations for this section are:
   1. Construct only four 12’ lanes with the 4’ bike lanes and sidewalks now. Construct the additional two 12’ lanes and add the curb and gutter in the future as needed.

TranSystems has conducted cost-benefit analyses of these three alternative cross sections. These analyses utilize the CAMPO regional traffic model to predict relative levels of service between the alternates. The analyses utilize the CAMPO Project Estimating Worksheets for Construction Costs to predict relative costs between the alternatives. The CAMPO model and worksheet were utilized to compare the alternatives based on one set of data.

TranSystems made the following recommendation at the March 3^rd Operations Committee meeting.

"Based on the total project cost and the traffic analysis, TranSystems recommends proceeding with the project as currently designed with modifications as deemed necessary by NCDOT and the Town during their reviews. Revisions from citizen input will also be considered. These changes could involve additional left turn lanes and/or right turn lanes. Also, the queue jump lanes could be included in the project.

The Town should consider amending the Thoroughfare along the Davis Drive corridor to be a six-lane roadway with a median of 12' to 30' wide for possible future expansion of the roadway."

The Operations Committee recommended that staff present further information at the council meeting for discussion by the full council. The additional information provided by the Consultant follows. This information will be presented at the April Operations Committee meeting and at the April 13th Town Council meeting.

M E M O R A N D U M

TO: Engineering Department, Town of Cary

FROM: Brian A. Wiles, P.E, TranSystems

SUBJECT: Additional Information
Project Number 30299020.00
TOC 99-040
Davis Drive Widening

DATE: March 28, 2000

Traffic Model: The traffic model used for traffic projections is the CAMPO regional model. The model bases the projected traffic on current land use and zoning of the area and an estimated growth rate for the region. The model uses an iterative process to assign vehicles to different roads based on paths of least resistance. The input into the model includes number of lanes for each section of roadway, origin and destination points for the vehicles.

The results for the model are valid for comparison between different alternates. The traffic volumes are relative to each other, but are not necessarily absolute numbers. The model uses the same assumptions and growth factors for all the alternates for the future years. If zoning or other factors changes the growth rate all the options would be affected in a similar manner.

Bike Lanes: Four-foot bike lanes inside the curb and gutter are included on alternates 2, 3 and 4. Four-foot bike lanes could be added to alternate 1 (current design) with a small increase to the construction cost and additional right-of-way needed for construction. The construction cost for the extra width for the bike lanes was not included in any of the alternates. If the five-foot concrete sidewalk was replaced by a ten-foot asphalt bike path outside of the curb and gutter, the construction cost would be approximately the same. The bike path outside of curb and gutter would be located a few feet behind the curb not winding around trees or up and down small hills. If the nonparallel bike path was desired more land would need to be acquired for this purpose.

Bike lanes inside of the curb would be more useful for "commuting" riders, whereas a bike lane behind the curb and away from traffic would probably be used by recreational riders or families. Commuting riders would not be as likely to use a lane behind the curb, because at every cross street they would need to negotiate ramps to get from the bike lane to the street and back.

Median Options: Alternate 1 The proposed median is a four foot raised concrete median.. NCDOT comprised their normal median standards, because Cary not NCDOT is going to pay for the Davis Drive widening project.

Alternates 3 and 4 A thirty-foot raised median was estimated for right-of-way and construction for this study. The median width could be reduced to sixteen feet and meet NCDOT guidelines. NCDOT might be willing to reduce this to twelve feet in areas that are fully developed and no left turn lanes will be added in the future. At the major intersections, i.e. High House and Morrisville-Carpenter road, the thirty-foot median should be maintained for the possibility of future dual left turn lanes.

Additional Information: If either alternate 3 or 4 is chosen as the typical section to use, then the number properties and amount of proximity damage could probably be reduced by modifications to the median width, alignment and/or retaining walls.