TRANSYT-7F

Did You Know?
Sample Input and Output Files
Release 9 and Release 10 Patches

Frequently Asked Questions

Why is a movement failing when it has plenty of green time?

When a movement is failing even though it has enough green time, this usually indicates queue spillback from a downstream intersection.   Use the wide output format to check "Time Full%" for the downstream links, or use the Profile View screen to check "Link Full Flag" for the downstream links.

How do I get rid of legacy report warning messages 161, 165, or 167, which say that the upstream and downstream flows are significantly unbalanced?

The "automatic flow balancing" feature within the Map View and the Feeders screen is usually helpful for balancing the upstream and downstream flows.  However, if these flow balancing warning messages persist even after using automatic flow balancing, it implies that large vehicle volumes are entering or leaving the roadway prior to the downstream signal.  If large vehicle volumes are entering the roadway from a mid-block source, these mid-block volumes should be coded on the Edit > Traffic screen, to achieve correct model results.  If large vehicle volumes are exiting the roadway at a mid-block source, feeding flows can optionally be reduced on the Edit > Feeders screen (to eliminate warning messages), but model results will not be affected.

What should I do if the program says "Relevant data could not be extracted from TRANSYT-7F output. Please check TRANSYT-7F input and output files for errors."

Go to the Edit > Analysis screen and switch from Optimization to Simulation.  Then perform a simulation-only run.  The legacy report should reveal any input coding errors that are interfering with the optimization process.

What is the best Performance Index to use for optimizing progression and bandwidth?

For optimizing bandwidth and progression speeds, PROS/DI is recommended.  PROS-only is rarely acceptable because although it produces a good bandwidth, the minor movements are allowed to fail.  Delay-only optimization results in excessive stops and fuel consumption.  Fuel Consumption (minimization) is considered to be a good compromise between bandwidth and delay-based optimization.  The Disutility Index (DI) is an effective combination of minimizing delay and stops, but rarely produces a wide bandwidth.  Other objective functions involving Throughput and Queuing Ratio should only be applied when conditions are severely oversaturated.

Why is the percentage of Total Stops sometimes reported as greater than 100%?

Random-plus-oversaturation stops represent partial stops following a phase failure, where there is not enough green time to serve the queue.  As such, individual vehicles could presumably stop multiple times (sometimes causing Total Stops% > 100%) before clearing the intersection, although these would not be considered "full stops" for the purposes of computing fuel consumption.  In order to be considered a full stop, a vehicle must transition between the cruise speed and zero speed.  TRANSYT-7F computes the fuel consumption due to random-plus-oversaturation stops differently than the fuel consumption due to uniform stops.  The model assumes that random-plus-oversaturation stops are made while vehicles are traveling at the queue speed (the one at which the queue dissipates), while uniform stops are assumed to be made from cruise speed.

What causes the following warning message: "The length of link 101 is not the same as the length of link 102".  This statement is true, but why is it a warning?

Link lengths affect the simulation of platoon dispersion.  Some users code short turn pocket storage lengths on the Edit > Traffic screen, but this could cause incorrect simulation of platoon dispersion, because platoons must travel all the way from the upstream signal to the downstream signal.  Therefore, even for turn pockets, link lengths on the Edit > Traffic screen should reflect the distance from upstream signal to downstream signal.  The best way to model turn pocket lengths (and queue spillover) is to code "Turn Bay Storage" values on the Edit > Lanes screen.

What causes “Processing Error 238”?

This error message was added to prevent cycle length optimization using the stand-alone engine (T7FWin2.exe).  A more robust methodology for cycle length optimization has been implemented externally (via TRANSYT-7F.exe).  Therefore, running the engine (T7FWin2.exe) in the stand-alone mode could cause error message #238.  Another thing that has caused the fatal error message for some users are input data files that have not yet been converted into release 10 or release 11 format.  To circumvent this problem, simply go to the Edit > Analysis screen within TRANSYT-7F.exe, and request cycle length optimization on this screen.

After running hill-climb cycle length optimization, or genetic algorithm optimization, how can I view the detailed output statistics?

To get the full output report for the optimal timing plan, it is necessary to load and run the punch (*.pun) file that was generated by the previous optimization run.

Does TRANSYT-7F report the average queue length in the output?

TRANSYT-7F reports the average or expected maximum back of queue length (including uniform queue, random queue, and residual queue).  Actual queue lengths in the field have a 50/50 chance of being higher or lower than the average queue length reported by the program.  Release 11 now provides 95th percentile maximum back of queues in the node summary reports.