Text from 'Traffic Impacts of Short Term Interstate Work Zone Lane Closures: The South Carolina Experience' PowerPoint Presentation

Slide 1

Traffic Impacts of Short Term Interstate Work Zone Lane Closures: The South Carolina Experience

Wayne Sarasua, Ph.D., P.E.

sarasua@clemson.edu

Slide 2 and 3

Overall Goals

Develop a means to determine an actual volume of vehicles per hour per lane to be used to determine when lane closures may be permitted.
Develop a means to estimate speeds, delays, and queue lengths due to short-term lane closures in work zones
Analyze the effects of roadway grades, truck percentages, and lane widths on work zone traffic characteristics when lane closures are present

Slide 4

Research Participants

Clemson University: Wayne Sarasua, David Clarke, and several GRAs
The Citadel: William J. Davis

Slide 5

Knowledge Acquisition and Literature Review

Strategy sessions
Comprehensive Literature Review
Survey of State DOTs

Slide 6

Classical Traffic Flow Theory

Diagram: Illustrates that for traffic flow to stay constant, the density of the road must increase in proportion to the decrease in speed.

Slide 7

Capacity Measurement

Maximum rate of flow (HCM)
Mean queue discharge rate
Hourly rate of flow under congested conditions
Flow rate at which traffic changes from uncongested to queued conditions

Slide 8

Traffic Measurement Techniques

Traffic Volume/Headway: Video surveillance, Inductive loops with counters, Road tubes with counters, and Inductive counters
Speed measurement: Road tubes and Radar or Laser

Slide 9

Factors Influencing Freeway Work Zone Capacity

Work zone configuration
Highway grade
Presence of freeway ramps
Traffic stream make-up
Weather conditions
Intensity/duration of construction activities
Lighting

Slide 10

Volume Thresholds

The following table shows the threshold lane volume for 7 states.

State	Threshold Lane Volume
Connecticut	1,500 - 1,800 vphpl
Missouri	1,240 vphpl
Nevada	1,375 - 1,400 vphpl (7% trucks)
Oregon	1,400 - 1,600 pcphpl
South Carolina	800 vphpl
Washington	1,350 vphpl
Wisconsin	1,600/2000 pcphpl (rural/urban)

Slide 11

Instrumentation and Field Data Collection

Design the surveillance setup, acquire hardware, and implement design
Field test and make adjustments
Field test at an actual interstate work zone
Collect data at various rural and urban work zone sites

Slide 12

Photo: Wind Research Tower

Slide 13

Surveillance Setup

Illustration: Tall tripods from SkyEye Corporation. One surveillance camera is pointed toward the flow of traffic; the other is pointed toward the Work Zone limits

Slide 14

Photo: Roadside Setup. Surveillance camera set up on tripod pointed toward flow of traffic

Slide 15

Photo: Base of tripod

Slide 16

Photo: Workers set up connecting cables on surveillance camera

Slide 17

Photo: Autoscope camera and pan/tilt unit

Slide 18

Photo: Workers raise the autoscope camera and pan/tilt unit on tripod

Slide 19

Photo: Tie-down and ground anchor for the tripod

Slide 20

Photo: Raised tripod

Slide 21

Photo: Tripod set up on a bridge

Slide 22

Photo: Great perspective view: a clear view of the road from the perspective of the tripod

Slide 23

Photo: Peripheral devices

Slide 24

Surveillance Setup Summary

Tripods are of adequate (not optimal) height
Stable, even in windy conditions.
Very flexible
Enhanced safety
Little or no effect on traffic operations
Need about an hour to setup completely
Breakdown takes about 1/2 hour

Slide 25

Projects

Collected data at 22 locations
First data collection on 9/12/01
Summary: I-85: 13 Projects; I-26: 6 Projects; I-77: 1 Project; and I-385: 2 Projects

Slide 26

Work Zone Project Log

The table below lists projects by number; date; start time and end time; interstate, direction, and MPP location; type of work; closure geometry; taper length; equipment activity (heavy or light); length of work (short or long), and weather conditions.

Project No.	Date	Time start	Time end	Location Interstate	Location Direction	Location MPP	Type of work	Closure geometry	Taper length	Equipment activity	Length of Work Zone	Weather conditions
1	09/12/01	19:15	21:15	85	N	32	Median Cable Guardrail	Inside lane of 2 closed	863	Light	Short	Warm, Clear
2	09/13/01	19:45	20:45	26	W	54	Median Cable Guardrail	Inside lane of 2 closed	795	Light	Short	Warm, Clear
3	09/16/01	19:40	21:15	85	S	8.5	Median Cable Guardrail	Inside lane of 2 closed	600	Light	Short	Warm, Clear
4	09/30/01	19:05	22:30	85	N	0	Median Cable Guardrail	Inside lane of 2 closed	665	Light	Short	Warm, Clear
5	10/01/01	9:00	18:00	77	N	80	Paving (OGFC)	Inside 2 lanes of 4 closed	675, 1475, 850	Heavy	Long	Warm, Clear
6	10/03/01	17:00	22:30	385	N	40	Paving (surface)	Outside lane of 2 closed	446	Heavy	Long	Warm, Clear
7	11/05/01	20:00	22:00	26	W	208	Final striping	Outside 2 lanes of 3 closed	668, 1544, 684	Heavy	Short	Cold, Clear
8	01/31/02	15:30	16:00	26	E	178	Concrete Pavement Repair	Outside lane of 2 closed	800	Heavy	Medium	Cool, Clear
9	03/11/02	16:00	18:10	385	W	2	Median Cable Guardrail	Inside lane of 2 closed	950	Light	Long	Cool, Clear
10	04/03/02	8:30	10:30	26	E	104	Median Cleanup	Inside lane of 3 closed	—	Light	Short	Warm, Clear
11	04/08/02	8:42	11:10	26	E	107	Median Cleanup	Inside lane of 4 closed	575	Light	Short	Warm, Clear
12	06/03/02	19:00	21:15	85	S	28	Paving	Inside lane 1 of 3 closed	800	Light		Clear
13	06/04/02	19:00	20:30	85	S	28	Rumble Strips	Inside lane 1 of 3 closed	—	Light		Clear
14	06/06/02	19:00	19:00	85	S	28		Inside lane 2 of 3 closed	800	Light		Clear
15	06/07/02			85	S		NA	NA	NA	NA	NA	Rain
16	06/13/02	19:00	21:00	85	S	28		Inside 1 lanes of 2 closed		Heavy		Warm, Clear
17	06/14/02	19:00	21:20	85	S	28	Concrete Paving	Outside lane of 2 closed	—	Heavy	Long	Warm, Clear
18	06/20/02	20:00	22:00	85	S	28	Concrete Paving	Outside lane of 2 closed	800	Heavy	Long	Warm, Clear
19	07/09/02	19:15	20:15	85	S	2	Bridge Maintenance	Outside lane of 2 closed		Light	Long	Warm, Clear
20	07/21/02	19:03	21:08	85	N	179	Bridge Maintenance	Outside lane of 2 closed		Light	Long	Warm, Clear
21	07/22/02	18:56	20:30	85	N	179	Bridge Decil Maintenance	Outside lane of 2 closed		Light	Long	Clear
22	08/23/02	21:00	22:00	26	W		Concrete Paving	Outside 2 lanes of 3 closed	800	Light	Long	Clear

NA=Data collection canceled due to weather conditions, after completion of equipment set-up.

Slide 27

Work Zone Project Summary Statistics for Vehicles

The table below lists statistics for vehicles including location, PC%, T%, minimum and maximum hourly volume, whether there is a queue, and the length of the queue.

Project No.	Location	PC%	T%	1-minute hourly volume (max)	1-minute hourly volume (min)	5-minute hourly volume (max)	5-minute hourly volume (min)	Hourly volume (max)	Hourly volume (min)	Queue?	Max Queue Length
1	I-85 N MPM32	64.33%	35.67	1980	60	1056	648	—		None	—
2	I-26 W MPM 54	71.05%	28.95	1320	120	648	324	497	445	None	—
3	I-85 S MPM 8.5	87.25%	12.75	2160	300	1572	636	1221	767	Few	3200
4	I-85 N MPM 0	82.63%	17.37	2100	120	1440	324	1320	995	Continuous	>1 mile
5	I-77 N MPM 80	84.56%	15.44	1410	450	1140	636	930	802	None	—
6	I-385 N MPM 40	96.83%	3.17	1140	120	744	60	553	458	None	—
7	I-26 W MPM 208	87.62%	12.38	1800	360	1308	576	1124	735	None	—
8	I-26 E MPM 178	84.45%	15.55	1680	360	1128	720	927	871	None	—
9	I-385 N MPM 2	84.49%	15.51	1320	0	696	276	565	509	None	—
10	I-26 E MPM 104	88.68%	11.32	2280	1140	2016	1266	1041	1041	Continuous	>4500
11	I-26 E MPM 107	91.06%	8.94	1722	678	1480	1044	1308	1152	None	—
12	I-85 S MPM 28	68.61%	31.39	1740	180	1284	636	1090	820	None	—
13	I-85 S MPM 28	72.68%	27.32	2220	180	1668	756	1251	976	Discontinuous	500
14	I-85 S MPM 28	73.69%	26.31	2100	480	1524	1008	1357	1141	Discontinuous	8000
16	I-85 S MPM 28	73.42%	26.58	2160	540	1500	936	1341	1047	Discontinuous	>1 mile
17	I-85 S MPM 28	82.79%	17.21	2280	120	1680	660	1504	1240	Continuous	>1 mile
18	I-85 S MPM 28	69.67%	30.33	1800	360	1452	732	1110	916	Continuous	3000
19	I-85 S MPM 02	66.93%	33.07	1800	240	1236	636	672	672	None	—
20	I-85 N MPM 179	85.96%	14.04	1980	120	1032	648	903	799	Continuous	>1mile
21	I-85 N MPM 179	65.57%	34.43	1800	300	1548	384	1339	867	None	—
22	I-26 W	90.40%	9.60	2100	420	1104	948	920	131	Discontinuous
Average		79.65%	20.35	1852	317	1298	660	1049	819

Work Zone Project Summary Statistics for Passenger Car Equivalents

The table below lists statistics for passenger car equivalents, including location, PC%, T%, minimum and maximum hourly volume, whether there is a queue and the length of the queue.

Project No.	Location	PC%	T%	1-minute hourly volume (max)	1-minute hourly volume (min)	5-minute hourly volume (max)	5-minute hourly volume (min)	Hourly volume (max)	Hourly volume (min)	Queue?	Max Queue Length
1	I-85 N MPM32	64.33%	35.67	3060	60	1560	1044	—		None	—
2	I-26 W MPM 54	71.05%	28.95	1680	180	882	492	702	640	None	—
3	I-85 S MPM 8.5	87.25%	12.75	2700	300	1824	726	1414	918	Few	3200
4	I-85 N MPM 0	82.63%	17.37	2280	120	1728	534	1540	1243	Continuous	>1 mile
5	I-77 N MPM 80	84.56%	15.44	1770	555	1389	765	1112	954	None	—
6	I-385 N MPM 40	96.83%	3.17	1500	120	768	60	572	479	None	—
7	I-26 W MPM 208	87.62%	12.38	2160	360	1506	666	1310	871	None	—
8	I-26 E MPM 178	84.45%	15.55	2010	450	1416	864	1107	1059	None	—
9	I-385 N MPM 2	84.49%	15.51	1710	0	918	312	689	608	None	—
10	I-26 E MPM 104	88.68%	11.32	2565	1245	2262	1446	1178	1178	Continuous	>4500
11	I-26 E MPM 107	91.06%	8.94	1968	738	1620	1152	1437	1284	None	—
12	I-85 S MPM 28	68.61%	31.39	2520	180	1758	1056	1518	1217	None	—
13	I-85 S MPM 28	72.68%	27.32	3510	270	2232	960	1640	1428	Discontinuous	500
14	I-85 S MPM 28	73.69%	26.31	2790	660	2202	1428	1836	1574	Discontinuous	8000
16	I-85 S MPM 28	73.42%	26.58	2790	210	2100	1296	1844	1441	Discontinuous	>1 mile
17	I-85 S MPM 28	82.79%	17.21	2640	120	2070	768	1793	1564	Continuous	>1 mile
18	I-85 S MPM 28	69.67%	30.33	2550	450	1998	1056	1552	1331	Continuous	3000
19	I-85 S MPM 02	66.93%	33.07	2070	330	1674	930	995	995	None	—
20	I-85 N MPM 179	85.96%	14.04	2670	210	1500	978	1332	1198	Continuous	>1mile
21	I-85 N MPM 179	65.57%	34.43	2190	360	1830	558	1536	1065	None	—
22	I-26 W	90.40%	9.60	2550	420	1338	1110	1038	149	Discontinuous
Average		79.65%	20.35	2366	349	1646	867	1307	1060

Slide 28

Data Collection

Night time data collection not ideal: Autoscope is not as effective and volumes are generally low except I-85
Difficult to obtain specific information on location of closure in advance
Setup and procedures adequate for providing data to meet project objectives

Slide 29

Data Analysis

Graph and analyze data
Develop predictive model as a function of known model parameters: Traffic and truck volumes, Length of lane closure, Lane widths, Shoulder characteristics, and Roadway grades

Slide 30

Underlying Concepts

Equation 1: k=q/s

where:

k = density (vehicles per mile)

q = flow (vehicles per hour)

s = speed.(mph)

Can also be expressed in terms of average vehicle spacing:

Equation 2: k=5280/spacing

Slide 31

An Example of Capacity

Given:

Speed limit for short term work zone projects in South Carolina is 45 mph.

Average spacing in saturated conditions for a speed of 45 mph is 150 feet per vehicle.

Using equation 2, k = 5280/spacing = 35.2 vehicles per mile.

From equation 1, q = ks = 35.1 * 45 = 1584 vehicles per hour.

Slide 32

Diagram from the Classical Traffic Flow Theory, for flow to stay constant, the density of the road must increase in proportion to the decrease in speed.

This indicates that at lower speeds, there is willingness for cars to travel at closer intervals. The table below indicates the speed in miles per hour and spacing of the traffic flow.

Speed	Spacing
45	150
40	133
35	117
30	100
25	83
20	67
15	50
10	33

Slide 33

Combining Data to Facilitate Analysis

No single project completely follows Greenshields' generalized form
Necessary to combine data
Difficult to isolate the characteristics of individual projects
Underlying assumption that all projects that were combined were homogeneous

Slide 34

Project Characteristics

Commonality: Rolling terrain except I-26 south of Columbia, 12-foot lane widths, Similar taper lengths
Differences: Type of maintenance activities, Work zone length, and Number of lanes downstream

Slide 35

Speed versus Flow: 2 to 1-lane

Scatter graph showing discrete 5-minute traffic flows.

With the mean speed at 45 miles per hour, traffic flow ranges from 400 to 1600 vph.

With the mean speed at 20 miles per hour, traffic flow ranges from 1000 and 1600 vph.

Slide 36

Speed versus Flow: 2 to 1-lane

Scatter graph showing 12 consecutive 5-minute periods.

With the speed ranging from 10 to 50 miles per hour, traffic flow ranges only slightly, from 1000 to 1400 vph.

Slide 37

Considering Heavy Vehicles

Research has shown that heavy vehicles have a significant effect on capacity
Must be considered on a case by case basis
Most common approach is applying passenger car equivalents (PCE)

Slide 38

Methodology for Determining PCE

Measured headways by analyzing video
Used software developed for project (Satflo2) to record time and vehicle type
Results are tabulated and graphed

Slide 39

Headway Frequencies by Vehicle Type

Bar chart: The trend line shows the number of headway occurrences increases dramatically (up to 65) in the first half-hour, decreases (down to 50) over the next half-hour, and then increases again (up to 85) after 1.5 hours. From there, the headway occurrences drop significantly (down to 35) at 2 hours and continue to decrease (with minor increases) through the 10 hours, with only 2 occurrences at hour 10.

Slide 40

Passenger Car Equivalents Grouped by Speed

The table below lists statistics for passenger car equivalents (RVs and trucks) grouped by speeds of less than 15 miles per hour, between 15 and less than 30 mph, between 30 and less than 45 mph, between 45 mph and less than 60 mph, and greater than 60mph.

Project	RV less than 15mph	Truck less than 15mph	RV 15 to less than 30mph	Truck 15 to less than 30mph	RV 30 to less than 45mph	Truck 30 to less than 45mph	RV 45 to less than 60mph	Truck 45 to less than 60mph	RV greater than 60mph	Truck greater than 60mph
13	0	0	1.52	1.68	1.28	1.66	1.4	1.75	1.11	1.79
14	1.32	1.89	1.62	2.06	1.39	2.14	1.66	1.92	1.52	1.85
16	0	0	1.23	2.42	1.5	2.14	1.44	2.14	1.26	2.06
17	1.2	2.09	1.33	2.22	1.5	2.48	1.67	2.75	0	0
18	1.37	2.04	1.42	2.03	1.6	1.95	1.41	2.02	1.44	2.12
20	1.68	2.21	1.59	2.2	1.98	2.18	1.28	2.02	1.7	2.62
21	0	0	0	1.27	1.95	1.98	1.58	1.85	1.22	1.91
7	0	0	0	0	1.58	2.01	0	0	0	0
10	0	0	1.16	2.13	1.16	1.89	1.06	0	0	0
11	0	0	0	1.83	0	0	1.46	1.87	1.15	2.2
5	0	0	0	0	1.4	1.86	0	0	0	0
All	1.414	1.948	1.414	2.085	1.497	1.986	1.511	1.940	1.375	1.991

Slide 41

Average Passage Car Equivalents (PCEs) Used in Analysis

The table below provides the number of sample passenger cars, RVs, and heavy trucks used in this study.

Type of Vehicle	Sample	Passenger Car Equivalent
Passenger Car	10293	1.00
RV	470	1.44
Heavy Truck	2019	1.93

Slide 42

Speed versus Flow: 2 to 1-lane

Scatter graph showing discrete 5-minute passenger car equivalents.

With the mean speed at 45 miles per hour, flow (pcph) ranges from 500 to 1700 vph. With the mean speed at 20 miles per hour, flow (pcph) ranges from 1200 and 1600 vph.

Slide 43

Speed versus Flow: 2 to 1-lane

Scatter graph showing 12 consecutive 5-minute periods (passenger car equivalents).

With the speed ranging from 10 to 50 miles per hour, flow ranges from 800 to 1700 vph.

Slide 44

Modeling Methodology

Model Speed versus Density Relationship
From the resulting linear model, substitute k=q/s
Determine maximum Flow in PCE
Adjust for other factors
Formulate model for application to specific short-term work zones

Slide 45

Speed versus Density: 2 to 1-lane

Scatter graph showing discrete 5-minute passenger car equivalents.

Speed= -0.3951 (Density) + 52.539

R squared (R2) = 0.8114

With the mean speed at 50 miles per hour, density ranges from 20 to 50 pcpmi.

With the mean speed at 10 miles per hour, density ranges from 60 and 150 pcpmi.

Slide 46

Speed versus Density: 2 to 1-lane

Scatter graph showing 12 consecutive 5-minute periods (passenger car equivalents).

Speed= -0.4931 (Density) + 54.108

R squared (R2) = 0.9536

With the speed ranging from 15 to 50 miles per hour, density ranges from 15 to 80 pcpmi.

Slide 47

Modeling Speed versus Flow

s = -0.395 k + 52.54 (5-minute discrete data)

s = -0.493 k + 54.11 (5-minute consecutive data)

Substituting k=q/s gives:

q= -2.53 s² + 133 s (5-minute discrete data)

q= -2.03 s² + 110.7 s (5-minute consecutive data)

where: q = flow (pcphpl)

s = speed (mph)

Slide 48

Speed versus Flow: 2 to 1-lane

Scatter graph showing discrete 5-minute passenger car equivalents.

With the mean speed at 50 miles per hour, flow ranges from 500 to 1700 pcph.

With the mean speed at 10 miles per hour, density ranges from 1000 and 1700 pcph.

Slide 49

Speed versus Flow: 2 to 1-lane

Scatter graph showing 12 consecutive 5-minute periods (passenger car equivalents).

With the speed ranging from 10 to 45 miles per hour, flow ranges from 600 to 1700 pcph.

Slide 50

Estimating Capacity

First derivative of the s versus q model is slope of the parabola

dq/ds = -5.06 s + 133 5-minute discrete data

dq/ds= -4.06 s + 110.7 5-minute consecutive data

Slope of the parabola at maximum flow = 0. Setting the above equations = 0 give the speeds at maximum flow.

Substituting into previous slide gives max flow (capacity):

1748 pcphl (5-minute discrete data)

1483 pcphl (5-minute consecutive data)

Slide 51

Considering Grades

HCM considers grades in calculating PCEs: We found little variation in PCEs
Most projects had rolling terrain with moderate grades rarely extending more than a 1/2 mile
We did do some stratification
HCM individual grade sections applicable

Slide 52

A Comparison of Stratified Data

Line graph: As speed decreases from 55 to 30 mph on I-85, flow increases from 0 to 1700 pcph. As speed further decreases from 30 mph to 5 mph on I-85, flow decreases from 1700 to 600 pcph.

As speed decreases from 50 to 25 mph on non I-85, flow increases from 0 to 1700 pcph

Slide 53

Considering Other Factors

Work zone activity - used regression models with dummy variables. Found no significance
Ramps - ramp volumes at sites with nearby on-ramps were typically low
Weather - adverse weather never experienced duringdata collection

Slide 54

Formulating Final Model - f_HV

HCM heavy vehicle adjustment factor:

Equation 3: f_HV= 1/1+[P_T(E_T-1) + P_RV(E_RV-1)]

where:

P_T = proportion of trucks,

P_RV = proportion of RVs and cars with trailers,

E_T = PCEs for trucks and buses, and

E_RV = PCEs for RVs and cars with trailers.

A first estimate of capacity (veh/hr/lane):

C' = 1480 *f_HV

Slide 55

Accounting for Number Lanes

Data indicates that using a simple factor based on the number of discharge lanes is appropriate. The capacity estimate becomes:

C'' = 1480 *f_HV* N

where:

C'' = C' adjusted based on the number of lanes open through the work zone (veh/hr) and N = number of lanes open through the work zone.

Slide 56

Accounting for Work Zone Activity

The HCM 2000 suggests adjusting base capacity up or down by 10% depending on whether or not the work zone activity is more or less than normal. Thus, final form becomes:

Equation 4: C_WZ = (1480 + I) *f_HV* N

where:

C_WZ = the estimated capacity of a short-term work zone (veh/hr),

f_HV= heavy vehicle adjustment factor,

N = number of lanes open through the work zone, and

Slide 57

Example

Given: planned 2 to 1-lane typical short-term lane closure

Peak volume of 1,100 veh/hour 18 % trucks, 2 % RVs

Should the closure be moved to the evening?

1. Calculate f_HV:Using PCE table, the E_Tand E_RVare 1.93 and 1.44 respectively. Using equation 3, f_HV = 0.85.

2.Calculate C_WZ: Assuming I = 0 for a typical closure and N= 1, using equation 4 yields C_WZ = 1,258 vehicles per hour.

3. Compare volume to capacity: the V/Cratio in this example works out to be 0.87 based

It is unlikely that the volume will reach capacity.

Slide 58

Rate of Queue Development

Equation 5: s_w = q₂-q_1/k₂-k₁

where:

s_wis the shock wave velocity (will be negative),

q₂is the discharge flow,

q₁demand flow (flow upstream of the work zone),

k₂density of the flow of the moving queue, and

k₁density of the flow before the queue.

Slide 59

Queue Example

Given: 2 to 1-lane short-term lane closure. Before the closure, volume is 1,500 vehicles per hour and the density is approximately 25 vehicles per mile. Work zone causes the flow to reduce to 1,000 vehicles per hour and a queue density of 100 vehicles per mile. What would the queue length be from the bottleneck 5 minutes after the queue initially forms?

Shock wave velocity = (1000-1500)/(100-25) = -6.7 mph.

After 5 minutes: -6.7mph * 5 min * 1hr/60 min = 0.56 miles. At 100 vehicles per mile, this would equal 56 vehicles in the queue.

Slide 60

Graphical Example

Diagram: Illustration of the above calculation. With volume at 1,500 vehicles per hour and with the flow reduced to 1,000 vehicles per hour, the queue length from the bottleneck 5 minutes after the queue initially formed would be 56 vehicles.

Slide 61

If the volume is below capacity, no queue will form.

If the volume exceeds capacity, two speeds are assumed:

< 100 pcphpl over capacity, speed is 35 mph

> 100 pcphpl over, speed drops to 15 mph

The density for different speeds in PCEs/mile is given by:

k= (s-54.1)/-0.493

Thus, k= 80 PCEs per mile at a speed of 15 mph. Because q=k*s, the discharge flow is 1200 pcphpl. For a given work zone duration, length of the queue can be estimated in a similar fashion to the previous example.

Slide 62

Conclusions

Setup works well
Not enough data for conclusive findings on effects of various factors
Projects showed interesting traffic phenomena
800 vphpl equates to 1232 pcphpl in the absolute worst case 30 % trucks with a PCE of 2.8. This is still more than 250 pcphpl less than the conservative base value (1480)