Memorandum

City of Lawrence

Public Works

TO:	Mike Wildgen, Dave Corliss, Debbie Van Saun
FROM:	Chuck Soules
Date:	January 13, 2005
RE:	Kasold Drive, Peterson Road to KTA

At their meeting on January 11, 2005 the City Commission received several alternatives for the construction of Kasold Drive. Staff was given the following direction:

1. Maintain unrestricted access at all intersecting roads.

2. Provide evaluation on capacity of 3-lane versus 4-lane facility.

3. Evaluate option presented at City Commission meeting: roundabout at Calvin Drive and Grand Vista Drive with 3-lane road section in between.

4. Evaluate possibility of providing additional medians between Calvin Drive and Grand Vista Drive to above numeral 3.

Capacity of Proposed Roadway Section to Carry Projected Traffic:

The following discussion is intended to address questions in regards to the ability of the proposed two lane roadway and single lane roundabouts to carry the projected year 2025 traffic demand on Kasold Drive north of Peterson Road. Some of the following language is taken directly from KDOT’s “Kansas Roundabout Guide” and the National Research Council Transportation Research Board’s “Highway Capacity Manual”.

Projected Traffic Volumes.

The City of Lawrence Planning Department has established the following Traffic Projections for this segment of Kasold Drive:

Year 2005 Average Daily Traffic - 3500 vehicles per day

Year 2015 Average Daily Traffic - 10180 vehicles per day

Year 2025 Average Daily Traffic – 15210 vehicles per day

Single Lane vs Multilane Roundabouts and Approach Lane Configuration.

Roundabout configuration is specified in terms of the number of entry and exit lanes needed on each approach to serve the design year traffic volumes. Future year design volumes should be used to determine the ultimate configuration of the roundabout to serve traffic on a twenty-year planning horizon.

Typically, roundabouts are identified in terms of the number of circulating lanes (i.e. single-lane, double lane. etc.). The number of circulating lanes required for a particular approach is usually equal to the number of entering lanes required on the largest approach. Therefore, if a four-lane roadway is constructed with two lanes in each direction then double-lane roundabouts would be required. For one lane of traffic in each direction, a single lane roundabout is appropriate. It is not desirable to transition from four lanes to two lanes at the roundabouts and back to four lanes between the two proposed roundabouts. Merging movements would require tapers of 350 feet and a merge section from two to one lane has less capacity than an uninterrupted single lane.

Comments received to date have generally not favored the use of dual lane roundabouts.

The FHWA and KDOT have established that urban single lane roundabouts like those proposed for this project have adequate service level for 20,000 vehicles per day, which indicates that the proposed roundabouts have a 31.5% excess capacity in the design year 2025. Multilane roundabouts produce increased capacity up to 40,000 to 50,000 vehicles per day, but also introduce additional conflict points and may have higher crash rates than single lane roundabouts. There is also greater local public concern about the drive-ability of dual lane roundabouts as opposed to single lane roundabouts. Therefore, the use of urban single-lane roundabouts is appropriate for this project.

Roadway Segment – Number of Lanes and Arterial Performance.

Capacity. The capacity of a two-lane roadway under ideal conditions is generally accepted as 2800 passenger cars per hour. By applying various factors pertaining to the proposed roadway improvements and assuming 5% trucks (standard), the year 2025 traffic is computed to have a service flow rate of 1860 passenger cars per hour. This indicates that in 2025 the two-lane roadway segment Kasold Drive will have excess capacity of 50 percent.

Planning Analysis to Determine the Number of lanes. Planning analysis was completed based upon the procedures outlined in the Highway Capacity Manual. The standard estimates used by KDOT of 11% for design hourly volume and a 60 – 40 for directional distribution were used. Based upon these factors, the number of lanes required in each direction to have Level of Service C in year 2025 computes as 0.9 Lanes. This rounds to one lane. Therefore, one lane of traffic in each direction should be acceptable for this segment of Kasold Drive.

Level of Service. In urban and suburban conditions, the capacity of arterial roadways is a function of the capacity of the intersections which generally are the points of constriction. Arterial level of service is based upon the average travel speed through the segment. This is the basic measure of effectiveness and there is no numeric computation of “arterial capacity.”

For a suburban arterial, the Highway Capacity Manual has defined Level of Service based upon average travel speeds, which includes delay at intersections. Average travel speeds are not mid block velocities, but the time it takes to travel an entire segment divided by the length of the segment.

Suburban Arterial

Level of Service Average Travel Speed

A greater than 35mph

B greater than 28 mph

C greater than 22 mph

D greater than 17 mph

E greater than 13 mph

F less than 13 mph

For two lane rural highways, the Highway Capacity Manual has defined level of service based upon the Average Speed rather than the Average Travel Speed. These level of service criteria are as follows:

Rural Two Lane Roadway – Level Terrain

Level of Service Average Speed

A greater than 58 mph

B greater than 55 mph

C greater than 52 mph

D greater than 50 mph

E greater than 45 mph

F less than 45 mph

A great deal variation exists between what drivers consider acceptable speeds on rural roads as opposed to those in urban areas. The year 2025 service flow rate for Kasold Drive determined as discussed above is 1860 passenger cars per hour. Using the speed density relationships defined in the Highway Capacity manual, speeds of 48 mile per hour are possible with the year 2025 traffic volumes. Under rural conditions, this would equate to a Level of Service E. However, neglecting intersection delay, this would be Level of Service A on a suburban arterial.

In summary, Kasold Drive from Peterson Road to the north configured with one through-lane in each direction and an auxiliary left turn lane at all intersections will have adequate capacity in the year 2025.

Upon review of the roundabout at Calvin Drive, the proximity of this intersection to Hutton Drive is too close and does not function well. Therefore, two additional options have been developed:

R-1: Beginning at the intersection of Peterson Road is a 5-lane section that will reduce to a 2-lane roundabout at Tillerman Drive. Between Tillerman Drive and Grand Vista Drive would be two 18-20 ft. single lanes (one each direction) with a 20 ft. median and full intersection at Huntington Drive.

R-2: Realignment of Calvin Drive to a 4-way intersection with Hutton Drive and construction of a roundabout, and two 18-20 ft. lanes with a 20 ft. median and intersections at Tillerman Drive and Huntington Road. A second roundabout at Grand Vista Drive would be constructed. This option would entail acquiring right-of-way for the realignment of Calvin Drive. Right-of-way acquisition is not a participating item with KDOT and would be 100% City cost. Calvin Drive will also have to be reconstructed.

The two new options presented provide the following advantages:

Sufficient capacity for design year traffic volumes.
Traffic calming.
Pedestrian crossings at roundabouts and at the intersection with Peterson Road.
Sufficient area within the median to provide for landscaping.
Access to neighborhoods.

Plan concepts and construction estimates will be available late Friday at http://www.lawrencepublicworks.org/annc-kasold-north.shtml and will be presented at the City Commission meeting.

Respectfully submitted,

Charles F. Soules, P.E.

Director of Public Works

CFS/je