Today we are continuing with the series of posts about calibrating SimTraffic. Travel times are often collected in the field and compared to the SimTraffic arterial report. If needed, speed can be calibrated either with the Link Speed in Synchro or the Speed Factor in SimTraffic.

Adding to our series about SimTraffic calibration, today's post focuses on the Turning Speed. Turning Speed is a simple item to code, but it can make a noticeable difference when modeling intersections with large turning radii or freeway ramps. This setting is a great place to start calibrating your SimTraffic model.

Make sure to read rest of the series; we have discussed Link OD Volumes, Lane Alignment, and the Positioning & Mandatory Distances.

We will be focusing on the westbound right turn of the intersection shown below. As you can see, it is a free-flowing channelized right-turn. With this type of geometry, drivers typically turn right at speeds approximately 5 to 8 mph higher than a typical non-channelized right turn (NCHRP 208).

Today's post is a continues our series on calibrating SimTraffic. Along with the Lane Alignment and Positioning Distances, the Link OD Volumes determine lane utilization in SimTraffic.

Located in the Volume Settings window, the Link OD Volumes window allows control over the origin and destination of two adjacent intersections. Link OD Volumes can be used to reduce or eliminate certain turn combinations, such as  preventing vehicles from turning left twice at a freeway or wide median arterial.

Lane Alignment is a simple, but important, calibration parameter for SimTraffic. This setting controls how the approach lane(s) align with the receiving lanes at an intersection, and is particularly important for locations with more receiving lanes than approach lane(s). Edit this setting in Synchro's Simulation Settings window; there are four possible choices:

• Left
• Right
• L-NA (left, no add)
• R-NA (right, no add)

When modeling a roadway with a large median, it can sometimes be difficult to determine if it should be modeled as one intersection with median or as two separate intersections. Ask yourself this question: 'Do drivers ever stop in the median?' If they do, then it should be modeled as two separate intersections. Let's look at a real life example...
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Here you can see two nearby intersections that are geometrically similar, but drivers are treating the median differently.

On the northern intersection, there are vehicles stopped in the median waiting to turn. You may also notice there are stop lines in the median, encouraging this behavior.

In contrast, drivers travel through the southern intersection with a single maneuver. There are no stop lines, and no vehicles stopped in the median.

In order to model this behavior in SimTraffic, the southern intersection should be modeled as one intersection with a median. The northern intersection should be modeled as two separate intersections, that may operate on a single controller using the Cluster Editor.

One of the best ways to calibrate the lane utilization in SimTraffic is using the Positioning and Mandatory Distances. This post will give you a good idea on when and how to use these settings to calibrate your model.

Traffic flow in SimTraffic is based on a series lane changing and car following algorithms. There are ten different driver types to provide various driver behaviors, including both aggressive and passive drivers. As vehicles are added to the network, they have a pre-determined path and already know several of their upcoming movements. This pre-determined path and the driver type will influence each driver’s lane change behaviors.

The decision on when a vehicle change lanes is based on two key parameters. The first is the Mandatory Distance and is defined as the distance from an intersection that a vehicle must have changed lanes to complete a required movement. If the vehicle has not changed lanes by this point, the vehicle will stop and wait for a gap. The second parameter is the Positioning Distance and is defined as the distance from the location of the Mandatory Distances that a vehicle will attempt to make a lane change to avoid being forced to complete a mandatory lane change. The figure below highlights the relationship of these parameters.

Before implementing a signal timing plan or construction project, you may be required to present your plan to the public, a client, coworkers, etc. To help with this, a new Screen Recorder feature is now included in SimTraffic Version 8.

To create a video in Synchro 9, selection Options⇒Video Recorder Parameters. The Video Recorder Parameters dialog will appear. Here you can select the desired codec, frames per second, and name the output file. Select OK.

Chose the Record Video button on the right side of the SimTraffic toolbar. While it is recording, a status message will display in the lower-left of the screen. To stop recording, press the Record Video button again.

“Should I use Synchro, SimTraffic, or both?” We often get this question from users. Today’s post discusses the benefits to help clarify the issue.

The “Choosing an Analysis Method” post from two weeks ago discussed the three macroscopic analysis methods available in Synchro: Percentile Method, HCM 2010, and HCM 2000. In addition to these choices, you can use SimTraffic for analysis.

The intention is to use Synchro and SimTraffic as companion models. Synchro can be used to determine macro level LOS and delays, then use SimTraffic to simulate realworld conditions. Not all projects require use of SimTraffic. Synchro analysis may be sufficient for a high-level planning study, for example.