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Publication Number: FHWA-HRT-04-131
Date: September 2004

Identifying and Assessing Key Weather-Related Parameters and Their Impacts on Traffic Operations Using Simulation

508 Captions

Figure 1. Study Approach. Diagram.

This figure shows a diagram containing a variety of information broken into five separate sections, each with their respective headings highlighted in yellow.

The first section is labeled Task A, Project Management. This section shows one block of information that reads Develop Work Plan, Deliverables, Schedule, and Staffing.

The second section is labeled Task B, Weather Impacts. This section shows three blocks of information, the first reading Conduct Literature Review and having two arrows, both leading to the additional blocks of information beneath it. The block of information to the left reads Investigate General Relationship between Weather Events and Traffic Operations, while the block of information to the right reads Review Past Research on Weather Impacts on Traffic Operations. Both the latter two blocks also have arrows leading from them to the next section of information.

The third section is labeled Task C, Identification of Parameters. This section shows one block of information that reads Identify Simulation Parameters Possibly Affected by Weather Events. An arrow leads from this block into the next section of information.

The fourth section is labeled Task D, Sensitivity Analysis. This section shows five blocks of information, the first reading Develop Automated Procedure for Generating and Summarizing CORSIM Runs and having two arrows, both leading to additional blocks of information beneath it. The block of information to the left reads Determine Which CORSIM Parameters to Include in Sensitivity Test, while the block of information to the right reads Code Test Networks and Volume Scenarios. Both the latter two blocks also have arrows leading from them to the next block of information, which reads Execute Sensitivity Test Runs and Summarize Results. This fourth block also has an arrow, which leads to the final block of information in this section, which reads Develop Guidance on Using CORSIM to Model Weather Events.

The final section is labeled Task E, Final Report. This section contains one block of information that reads Incorporate All Deliverables and FHWA Comments into Final Report.

Figure 2. Relationship Between Weather Events and Traffic Operations. Diagram.

This figure shows a diagram containing four blocks of information highlighted in yellow with several lines of information set off to the right hand side of the diagram itself. The first block of information reads Weather Event Occurs and has an arrow leading to the next block, which reads Weather Even Impacts Roadway Environment. The latter block has an arrow leading to the next block, which is highlighted additionally along with the block following it, both labeled "Traffic Operations". The first block in this section reads Change in Traffic Parameters (Input to Traffic Model) and has arrow leading to the final block, which reads Change in Quality of Traffic Flow (Output from Traffic Model).

The lines of information to the right of the diagram relate directly to each individual block of information inside the diagram. The first line reads Major snowstorm, relating to the block titled Weather Event Occurs.

The next three lines read Reduced pavement friction, Reduced driver visibility, and Snow bank blocks shoulder and right lane, relating to the block titled Weather Event Impacts Roadway Environment.

The next three lines read Lower free-flow speeds, More cautious lane changing and car following behavior, and Reduced number of lanes, relating to the block titled Change in Traffic Parameters.

The final three lines read Reduced capacity, Lower average speed, and Higher delays and stops, relating to the block titles Change in Quality of Traffic Flow.

Figure 3. NETSIM Suburban Intersection Network. Illustration.

This illustration shows an illustration of a traffic intersection, the background of the illustration in green and the lanes of traffic in black, crossing in the center of the illustration. The illustration shows two lanes coming from the left-hand side which extend to three lanes before the intersection, allowing for traffic to turn left, go straight, or turn right, and extends through the intersection, returning back to two lanes. Working clockwise around the illustration, it also shows two lanes from the top allowing for traffic to turn right, left or continue straight through the intersection where the lanes merge into a single lane. From the right hand side, two lanes extend to three prior to the intersection, allowing for traffic to turn left, right, or continue straight through the intersection where the three lanes return to two. Finally, the illustration shows a single lane from the bottom extending into three lanes, allowing for traffic to turn left, right, or continue straight through the intersection where the three lanes reduce to two lanes.

Figure 4. NETSIM Urban Intersection Network. Illustration.

This illustration shows an illustration of a traffic intersection, the background of the illustration in green and the lanes of traffic in black, crossing in the center of the illustration. The illustration shows a single lane coming from the left-hand side which extends to two lanes before the intersection, allowing for traffic to turn left, go straight, or turn right, and extends through the intersection, returning back to a single lane. Working clockwise around the illustration, it also shows a single lane from the top allowing for traffic to turn right, left, or continue straight through the intersection. From the right hand side, a single lane extends to two prior to the intersection, allowing for traffic to turn left, right, or continue straight through the intersection where the two lanes return to one single lane. Finally, the illustration shows a single lane from the bottom, allowing for traffic to turn left, right, or continue straight through the intersection.

Figure 5. Analysis Area Information for Sample Sensitivity Test. Diagram.

This figure shows a small diagram. The diagram has three lines tipped with arrows leading from the left-hand side to the right. The analysis area is highlighted in yellow and is labeled "analysis area". The bottom of the diagram hosts three lines of information relative to the analysis. The first line reads Freeway Lanes: 3. The second reads Analysis Area Length: 5.1 kilometers. Finally, the third line reads Freeway Free-Flow Speed: 113 kilometers per hour.

Figure 6. Vehicle-Kilometers traveled graph for Sample Sensitivity Test. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 100. The second is blue dashed with hollow blue diamonds and is labeled 125. The third is red with solid red triangles and is labeled 150. The fourth is green dashed with solid green dots and is labeled 175. Finally, the fifth line is purple with purple stars and is labeled 200. The vertical axis of this graph ranges from 0 to 40,000 and represents Vehicle-Kilometers of Travel in vehicle-kilometers per hour. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin at the points of just below 20,000 on the vertical axis and 1,000 on the horizontal axis.

The first line, black with diamonds inclines in a straight line to the point of 30,000 on the vertical axis and 2,000 on the horizontal axis where it plateaus and comes to an end at 30,000 on the vertical axis and 2,500 on the horizontal axis.

The second line, blue dashed with diamonds inclines in a straight line to the point of 29,000 on the vertical axis and 2,000 on the horizontal axis where it plateaus and comes to an end at 29,000 on the vertical axis and 2,500 on the horizontal axis.

The third line, red with triangles inclines in a straight line to the point of 28,000 on the vertical axis and 2000 on the horizontal axis where it plateaus and comes to an end at 28,000 on the vertical axis and 2,500 on the horizontal axis.

The fourth line, green dashed with dots inclines in a straight line to the point of 25,000 on the vertical axis and 1,500 on the horizontal axis where it continues to climb to 26,000 on the vertical axis and 2,000 on the horizontal axis. From this point the line plateaus and comes to an end at the point of 26,000 on the vertical axis and 2,500 on the horizontal axis.

The fifth line, purple with stars inclines in a straight line to the point of 25,000 on the vertical axis and 1,500 on the horizontal axis where it runs in a straight line an ends at the points of 25,00 on the vertical axis and 2,500 on the horizontal axis.

Figure 7. Average Speed Graph for Sample Sensitivity Test. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 100. The second is blue dashed with hollow blue diamonds and is labeled 125. The third is red with solid red triangles and is labeled 150. The fourth is green dashed with solid green dots and is labeled 175. Finally, the fifth line is purple with purple stars and is labeled 200. The vertical axis of this graph ranges from 0 to 120 and represents Average Speed in kilometers per hour. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin at the points of just below 100 on the vertical axis and 1000 on the horizontal axis.

The first line, black with diamonds, extends in a straight line from its starting point then begins to descend from 100 kilometers per hour at an entering volume of 1,500 until it comes to an end at 78 kilometers per hour at an entering volume of 2,500 on the horizontal axis.

The second line, blue dashed with diamonds extends in a straight line from its starting point then begins to descend from 100 kilometers per hour at an entering volume of 1,500 to the point of 62 kilometers per hour at an entering volume of 2,000. From this point the line plateaus and comes to an end at 62 kilometers per hour at an entering volume of 2,500 on the horizontal axis.

The third line, red with triangles extends in a nearly straight line from its starting point then begins to descend from 100 kilometers per hour at an entering volume of 1,500 to the point of 60 kilometers per hour at an entering volume of 2,000. From this point the line plateaus and comes to an end at 60 kilometers per hour at an entering volume of 2,500.

The fourth line, green dashed with dots extends from its starting point, descending almost immediately to 70 kilometers per hour at an entering volume of 1,500 where it continues to descend to 58 kilometers at an entering volume of 2,000. From this point the line plateaus and comes to an end at 58 kilometers per hour at an entering volume of 2,500.

The fifth line, purple with stars extends from its starting point descending dramatically to 60 kilometers per hour at an entering volume of 1,500. From this point the line descends gradually and comes to an end at 58 kilometers per hour at an entering volume of 2,500.

Figure 8. Average Delay Graph for Sample Sensitivity Test. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 100. The second is blue dashed with hollow blue diamonds and is labeled 125. The third is orange with solid orange triangles and is labeled 150. The fourth is green dashed with solid green dots and is labeled 175. Finally, the fifth line is purple with purple stars and is labeled 200. The vertical axis of this graph ranges from 0 to 200 and represents Average Delay in seconds per vehicle. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin near the points of zero seconds per vehicle on the vertical axis, at an entering volume of 1,000 on the horizontal axis.

The first line, black with diamonds extends from its starting point to 10 seconds per vehicle at an entering rate of 1,500 where it increases continually an comes to an end at 90 seconds per vehicle at an entering rate of 2,300.

The second line, blue dashed with diamonds, extends from its starting point to 15 seconds per vehicle at an entering volume of 1,500 where it increases to 110 seconds per vehicle at an entering volume of 2,000 and then plateaus until it comes to an end at 110 seconds per vehicle at an entering volume of 2,300.

The third line, orange with triangles, extends from its starting point to 20 seconds per vehicle at an entering volume of 1,500 where it increases to 130 seconds per vehicle at an entering volume of 2,000 and then plateaus until it comes to an end at 130 seconds per vehicle at an entering volume of 2,300.

The fourth line, green dashed with dots, extends from its starting point, increasing immediately to 40 seconds per vehicle at an entering volume of 1,500 where it continues to increase to 150 seconds per vehicle at an entering volume of 2,000 and then plateaus until it comes to an end at 150 seconds per vehicle at an entering volume of 2,300.

The fifth line, purple with stars, extends from its starting point increasing dramatically to 140 seconds per vehicle at an entering volume of 1,500 where it continues to increase to 170 seconds per vehicle at an entering volume of 2,000. From this point the line decreases slightly, coming to an end at 160 seconds per vehicle at an entering volume of 2,300.

Figure 9. Average Density Graph for Sampling Sensitivity Test. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 100. The second is blue dashed with hollow blue diamonds and is labeled 125. The third is orange with solid orange triangles and is labeled 150. The fourth is green dashed with solid green dots and is labeled 175. Finally, the fifth line is purple with purple stars and is labeled 200. The vertical axis of this graph ranges from 0 to 35 and represents Average Density in vehicles per kilometer per lane. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin near the points of near an Average Density of 10 on the vertical axis, at an Entering Volume of 1,000 on the horizontal axis.

The first line, black with diamonds gradually inclines across the graph until it comes to an end at an Average Density of 32 with an Entering Volume of 2,300.

The second line, blue dashed with diamonds, increases from its starting point and rises to an Average Density of 15 with an Entering Volume of 1,500 where it then increases again to an Average Density of 32 with an Entering Volume of 2,000. From this point the line plateaus and comes to an end with an Average Density of 32 at an Entering Volume of 2,300.

The third line, orange with triangles, increases from its starting point to an Average Density of 15 with an Entering Volume of 1,500 where it then continues to increase to an Average Density of 33 with an Entering Volume of 2,000. From this point the line plateaus and comes to an end with an Average Density of 33 at an Entering Volume of 2,300.

The fourth line, green dashed with dots, increases from its starting point to an Average Density of 17 with an Entering Volume of 1,500 where it then continues to increase to an Average Density of 32 with an Entering Volume of 2,000. From this point the line plateaus and comes to an end with an Average Density of 32 at an Entering Volume 2,300.

The fifth line, purple with stars, increases dramatically from its starting point to an Average Density of 27 with an Entering Volume of 1,500 where it then continues to increase, only gradually at this point, to an Average Density of 32 with an Entering Volume of 2,000. From this point the line plateaus and comes to an end with an Average Density of 32 at an Entering Volume of 2,300.

Figure 10. Sensitivity of Pitt Car Following constant on Freeway System Network-Example of "Expected" Sensitivity Group. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 10. The second is blue dashed with hollow blue diamonds and is labeled 12. The third is orange with solid orange triangles and is labeled 15. The fourth is green dashed with solid green dots and is labeled 17. Finally, the fifth line is purple with purple stars and is labeled 20. The vertical axis of this graph ranges from 0 to 120 and represents Average Speed in kilometers per hour. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin near the points of near an Average Speed of 105 on the vertical axis, at an Entering Volume of 1,000 on the horizontal axis.

The first line, black with diamonds, gradually decreases along the graph until it comes to an end at an Average Speed of 76 with an Entering Volume of 2,300.

The second line, blue dashed with diamonds, gradually decreases from its starting point to an Average Speed of 103 at an Entering Volume of 1,500 where it continues to decrease to an Average Speed of 76 at an Entering Volume of 2,000. From this point the line plateaus and comes to an end with an Average Speed of 76 with an Entering Volume of 2,300.

The third line, orange with triangles, decreases from its starting point to an Average Speed of 103 at an Entering Volume 1,500 where it then continues to decrease to an Average Speed of 74 at an Entering Volume of 2,000. From this point the line plateaus and comes to an end at an Average Speed of 74 with an Entering Volume of 2,300.

The fourth line, green dashed with dots, decreases from its starting point to an Average Speed of 103 at an Entering Volume of 1,500 where it then continues to decrease to an Average Speed of 72 at an Entering Volume 2,000. From this point the line plateaus and comes to an end at an Average Speed of 72 with an Entering Volume of 2,300.

The fifth line, purple with stars, decreases from its starting point to an Average Speed of 103 at an Entering Volume of 1,500 where it then continues to decrease to an Average Speed 72 at an entering Volume of 2,000. From this point the line plateaus and comes to an end at an Average Speed 72 with an Entering Volume of 2,300.

Figure 11. Sensitivity of Maximum Emergency Deceleration on Freeway System Network-Example of "Inconsistent" Sensitivity Group. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 4.57. The second is blue dashed with hollow blue diamonds and is labeled 3.96. The third is orange with solid orange triangles and is labeled 3.35. The fourth is green dashed with solid green dots and is labeled 2.74. Finally, the fifth line is purple with purple stars and is labeled 2.13. The vertical axis of this graph ranges from 0 to 120 and represents Average Speed in kilometers per hour. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin near the points of near an Average Speed of 105 on the vertical axis, at an Entering Volume of 1,000 on the horizontal axis.

The first line, black with diamonds, gradually decreases to an Average Speed of 80 at an Entering Volume of 2,000 where it then plateaus and comes to an end with an Average Speed of 80 at an entering Volume of 2,300.

The second line, blue dashed with diamonds, gradually decreases across the graph from its starting point to an Average Speed of 76 with an entering volume of 2,300 where it comes to an end.

The third line, orange with triangles, decreases to an Average Speed of 96 at an Entering Volume of 2,000 where it continues to decrease to an Average Speed of 76 with an Entering Volume of 2,300, coming to an end.

The fourth line, green dashed with dots, gradually decreases across the graph from its starting point to an Average Speed of 76 with an entering volume of 2,300 where it comes to an end.

The fifth line, purple with stars, gradually decreases to an Average Speed of 100 at an Entering volume of 1,500 where it then begins to decreases dramatically across the graph, coming to an end at an Average Speed of 62 with an Entering Volume of 2,300.

Figure 12. Sensitivity of Jerk Value on Freeway System Network-Example of "No Effect" Sensitivity Group. Graph.

This figure shows a graph with five distinct lines. The legend at the bottom of the graph shows the five distinct lines. The first line is black with solid diamonds and is labeled 2.13. The second is blue dashed with hollow blue diamonds and is labeled 1.83. The third is orange with solid orange triangles and is labeled 1.52. The fourth is green dashed with solid green dots and is labeled 1.22. Finally, the fifth line is purple with purple stars and is labeled 0.91. The vertical axis of this graph ranges from 0 to 120 and represents Average Speed in kilometers per hour. The horizontal axis of this graph ranges from 1,000 to 2,500 and represents Entering Volume in vehicles per hour per lane. All five lines begin near the points of near an Average Speed of 105 on the vertical axis, at an Entering Volume of 1,000 on the horizontal axis.

All five lines on this graph follow the same path across the graph, decreasing from their starting point to an Average Speed of 103 with an Entering Volume of 1,500. The lines then continue to decrease to an Average Speed of 80 with an Entering Volume of 2,000. From this point, the lines decrease further and come to an end at an Average Speed of 72 with an Entering Volume 2,300.

Figure 13. Microsimulation Model Development and Application Process. Diagram.

This figure shows a variety of information broken into four separate sections, each with their respective headings.

The first section, labeled Work Prior to Actual Modeling, contains two blocks of information. The first block, labeled 1 has a heading that reads Scope Project. The five lines of information beneath the heading read Define project purpose, Identify influence areas, Select approach, Select model, and Estimate staff time. The second block, labeled 2 has a heading that reads Data Collection. The three lines of information beneath the heading read Traffic volumes, Base maps/inventory, and Field observations.

The second section, labeled Initial Modeling contains three blocks of information. The first block, labeled 3 has a heading that reads Base Model Development. The two lines of information beneath the heading read Input data and Develop quality assurance. The second block of information, labeled 4 has a heading that reads Error Checking. The two lines of information beneath the heading read Review input and Review animation. The third block of information is highlighted and reads Working Model Before Calibration.

The third section, labeled Calibration, contains five blocks of information. The first block, labeled 5 has a heading that reads Compare Model MOEs to field Data.The two lines of information beneath the heading read Volumes and speeds match? and Congestion in right places?. The next block of information is questioning the result from the above block. Its heading reads Acceptable Match?. If an acceptable match is not the result, the next block reads No. Following the "No" block is the correcting block of information with a heading that reads Adjust Model Parameters. The three lines of information beneath the heading read Modify global parameters, Modify link parameters, and Modify route choice parameters. If an acceptable match between model MOEs and field data was indeed found, the next block of information reads Yes, Calibrated Model.

The fourth and final section, labeled Model application, contains two blocks of information. The first block, labeled 6 has a heading that reads Alternatives Analysis. The three lines of information beneath the heading read Forecast demand, Base case, and Project alternatives. The second block, labeled 7 has a heading that reads Final Report. The two lines of information beneath the heading read Key results and Technical documentation.

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