Problem 4: Clifton Country Rd/Route 146 Intersection Base Case Phasing and Volumes Analysis Plans Description of Analyses Overarching Issues 4a: AM peak

Problem 4: Clifton Country Rd/Route 146 Intersection

Base Case Phasing and Volumes

Analysis Plans Description of Analyses

Overarching Issues 4a: AM peak hour -

Existing Conditions 4b: PM peak hour -

Existing Conditions 4c: 2004 PM - With vs

Without Conditions

The main question at this intersection will be: are geometric changes and/or adjustments in signal timing needed to accommodate the site-generated traffic?

Characteristics of the Clifton Country Rd intersection

Fully actuated signaling

EB approach is 5 lanes wide (left, triple through & signalized right)

WB approach is 5 lanes wide (double left, double through & free right)

SB approach has 3 lanes (left, left/through, & right/through)

NB approach has 4 (double left, through & free right)

2 large shopping complexes on each side of intersection

Major interchange with I-87 ~1/10 mile east of intersection

Observations?

Highest volumes on

EB & WB approaches

High volumes in the PM Peak

Sub-problem 4a: Clifton Country Road AM peak hour - Existing Conditions

AM existing conditions will be used to examine:

Lane utilization Coordination Lane group definitions

Lane Utilization

L T R Tot L T R Tot L T R Tot L T R Tot

Delay 34.5 28.6 10.2 25.6 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 32.3 32.0 25.9

v/c 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -

95-Queue 0.2 15.6 5.3 - 6.9 20.0 - - 4.4 2.2 3.2 - 4.4 - -

Queue 0.1 8.3 2.6 - 3.5 11.0 - - 2.1 1.1 1.6 - 2.2 - -

Delay 34.5 22.5 10.2 20.5 30.9 19.6 12.9 22.4 33.2 32.0 33.2 33.0 32.3 32.0 23.4

v/c 0.0 0.6 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -

95-Queue 0.2 13.1 5.3 - 6.9 19.1 - - 4.4 2.2 3.2 - 4.4 - -

Queue 0.1 6.8 2.6 - 3.4 10.4 - - 2.2 1.1 1.6 - 2.2 - -

1.0 0.7 1.0 - 0.9 0.9 1.0 - 1.0 1.0 1.0 - 1.0 -

Exhibit 2-40. Clifton Country Road Effects of Lane Utilization

Condition*Performance

Measure

Eastbound Westbound Northbound SouthboundOA

31.2

0.2

2.5

1.2

Observed Lane Utilization 1.0

Dataset 33 No Lane Utilization

31.2

0.2

2.5

1.2

Dataset 32 Base Case

The EB through is the movement where it is most important to use the real lane utilization

Why is that?

The real lane utilization is so different from the HCM default

Coordination


Delay 34.5 28.6 10.2 25.6 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 32.3 32.0 25.9

v/c ratio 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -

95-Queue 0.2 15.6 5.3 - 6.9 20.0 - - 4.4 2.2 3.2 - 4.4 - -

Queue 0.1 8.3 2.6 - 3.5 11.0 - - 2.1 1.1 1.6 - 2.2 - -

Delay 34.5 20.1 2.4 17.2 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 32.3 32.0 22.6

v/c ratio 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -

95-Queue 0.2 14.2 1.7 - 6.9 20.0 - - 4.4 2.2 3.2 - 4.4 - -

Queue 0.1 7.5 0.8 - 3.5 11.0 - - 2.1 1.1 1.6 - 2.2 - -

Delay 34.5 37.1 18.0 33.9 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 32.3 32.0 29.1

v/c ratio 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -

95-Queue 0.2 16.5 8.1 - 6.9 20.0 - - 4.4 2.2 3.2 - 4.4 - -

Queue 0.1 8.8 4.1 - 3.5 11.0 - - 2.1 1.1 1.6 - 2.2 - -

Exhibit 2-41. Clifton Country Road Impacts of Coordination on the Eastbound Approach

Condition*Performance

Measure



31.2

0.2

2.5

1.2

Dataset 34 Arrival Type 5 EB

TH&RT

31.2

0.2

2.5

1.2

Dataset 35 Arrival Type 1 EB

TH&RT

31.2

0.2

2.5

1.2

What are the effects of changing the Arrival Type from 3 to 5?

Reduction in EB delays and queue length

What if we assume the coordination is worse than random arrivals?

Significant increase in delay, which also means longer queues

Lane Group Definitions

The HCM is capable of analyzing many different lane groupings: exclusive lefts (one, two, three, etc.

lanes) shared left-and-through lanes through lanes shared right-and-through lanes exclusive rights

But it cannot do lane-by-lane analyses, and there are some lane groups that it doesn’t accommodate easily

Lane Group Definitions

The southbound approach has the following lane configuration: left, left/through through/right

The HCM doesn’t provide for an exclusive left-turn lane in conjunction with a left/through lane.

So what do you do?

Two criteria must be satisfied: 1) the innermost lane gets as much use as the center lane and the outermost lane gets very little use. 2) the queue lengths on the innermost lane and center lane are about balanced.

Based on the analysis this approach seems to be consistent with field observations

Sub-problem 4b: Clifton Country Road PM peak hour - Existing Conditions

PM existing conditions will be used to examine:

Lost time Demand vs. Volume Right turns on red

Lost Time

Start-up lost time is the initial green time that is not effectively used due to the perception, reaction, and start-up times required by the lead vehicles.

What is the HCM default for lost time?

2 seconds

What is the extension of effective green time?

The number of seconds, after the yellow interval begins, that vehicles are still entering the intersection

What is the HCM default for the extension of effective green time?

2 seconds

What are the effects of having both values the same? Different?

Demand vs. Volume

Intersection turning counts yield volumes, whereas arrival counts yield demand

Congested intersections have demand/volume ratios > 1.0 during the peak hour.

What happens when the ratio becomes larger than 1.0?

Queues begin to form and grow when the demand to capacity (D/C) ratio is greater than 1.0. Queues begin to dissipate when the D/C ratio falls below 1.0.

Demand vs. Volume


Delay 41.8 50.4 14 40.9 52.3 20.4 13.1 32.4 37.3 50.5 54.7 45.5 53.2 48.5 39.9

v/c ratio 0.4 0.97 0.45 - 0.92 0.69 - - 0.69 0.81 0.82 - 0.91 - -

95-Queue 1.8 20 11.4 - 16.7 18.9 - - 9 12.5 10.6 - 14.5 - -

Queue 0.9 10.9 5.9 - 9 10.3 - - 4.6 6.5 5.5 - 7.7 - -

Exhibit 2-43. Clifton Country Road PM Existing Base Case Conditions

Performance Measure



84

35.7

0.6

8.9

4.5

ConditionCycle Length

What observations can be made for this intersection?

High delays and fairly high v/c ratios Near capacity

For the with-site condition, the D/C ratio should be checked; mitigation will probably be necessary if it exceeds 1.0

Right Turns on Red


Delay 41.8 50.4 14 40.9 52.3 20.4 13.1 32.4 37.3 50.5 54.7 45.5 53.2 48.5 39.9

v/c ratio 0.4 0.97 0.45 - 0.92 0.69 - - 0.69 0.81 0.82 - 0.91 - -

95-Queue 1.8 20 11.4 - 16.7 18.9 - - 9 12.5 10.6 - 14.5 - -

Queue 0.9 10.9 5.9 - 9 10.3 - - 4.6 6.5 5.5 - 7.7 - -

Delay 41.8 50.4 14.5 40.3 52.3 20.4 16.3 30 37.3 50.5 79.7 52.7 53.2 48.5 39.7

v/c ratio 0.4 0.97 0.5 - 0.92 0.69 0.39 - 0.69 0.81 0.95 - 0.91 - -

95-Queue 1.8 20 13 - 16.7 18.9 9.1 - 9 12.5 13.9 - 14.5 - -

Queue 0.9 10.9 6.8 - 9 10.3 4.6 - 4.6 6.5 7.3 - 7.7 - -

Dataset 39 Downward

Adjusted RTOR85

35.7

0.6

8.9

4.5


84

35.7

0.6

8.9

4.5

Exhibit 2-44. Clifton Country Road PM Peak Hour Effects of RTOR

ConditionCycle Length

Performance Measure


What observations can be made about right turns on red?

For the EB approach 10% of the right turning vehicles turn on red

For the WB approach all of them are expected to turn on red since there is a separate right-turn auxiliary lane & not much opposing traffic

For the NB approach we assume as many vehicles turn right during phases 1 & 2 as WB lefts in a single lane (550/2)

Sub-problem 4c: Clifton Country Road 2004 PM - With vs. Without Conditions

EB WB NB L T R Tot L T R Tot L T R Tot L T R Tot

Delay 49 55 16 45 56 21 14 34 42 57 60 51 62 56 44

v/c 0.5 1 0.5 - 0.9 0.7 - - 0.7 0.8 0.8 - 0.9 - -

95-Queue 2.1 23 13 - 19 21 - - 10 15 12 - 17 - -

Queue 1 13 6.9 - 10 12 - - 5.4 7.7 6.3 - 9.2 - -

Delay 51 54 17 51 65 26 15 40 50 61 64 56 67 61 50

v/c 0.4 1 0.5 - 1 0.8 - - 0.8 0.8 0.8 - 0.9 - -

95-Queue 2.5 28 16 - 21 27 - - 13 16 13 - 19 - -

Queue 1.2 16 8.6 - 12 16 - - 7 8.5 7 - 10 - -

Delay 52 56 17 53 68 26 15 41 53 62 66 58 70 63 51

v/c 0.4 1.1 0.5 - 1 0.8 - - 0.8 0.8 0.8 - 0.9 - -

95-Queue 2.6 29 17 - 22 29 - - 14 16 14 - 19 - -

Queue 1.3 17 8.9 - 12 16 - - 7.4 8.7 7.1 - 10 - -

Delay 48 33 7.7 27 48 28 17 35 46 52 55 49 49 47 37

v/c 0.4 0.9 0.6 - 0.9 0.8 - - 0.8 0.8 0.8 - 0.8 - -

95-Queue 2.4 22 9.5 - 19 28 - - 13 15 12 - 16 - -

Queue 1.2 12 4.9 - 10 16 - - 6.7 7.8 6.4 - 8.6 - -

Exhibit 2-46. Clifton Country Road Scenario Investigations-Without & With Site-Generated Traffic

ConditionsCycle

Length

RTOR Performance Measure


Dataset 40 Without

95 39 267 340

40.6

0.63

10.5

5.4

Dataset 41 With Conditions Base

Case107 43 267 340

45.6

0.63

11.8

6.1

With Conditions 30% Higher Site

Traffic108 44 267 340

46.4

0.64

11.9

6.2

Dataset 43 With Conditions 30%

Higher Site Traffic-

enhanced

101 44 267 340

39.4

0.57

10.8

5.6

What has been done here? What can be done?

Observations?

Conclusions and Observations

This problem has explored a number of capacity modeling issues in the context of the Clifton Country Road intersection.

We examined time periods, the relationships among HCM methodologies, times to use other tools, and interpretation of results.

We examined lane groups and lost times.

We explored issues of queue spillback, feasibility of identified solutions, demand versus volume and right turns on red.

In the PM with-site condition, we focused on feedback the impacts of various assumptions about the future conditions and the tie between geometric changes and intersection performance.

Documents

Problem 4: Clifton Country Rd/Route 146 Intersection Base Case Phasing and Volumes Analysis Plans Description of Analyses Overarching Issues 4a: AM peak