FAQ

Program

How do I determine which version of Rodel I have?

The version will be displayed as soon as you open Rodel. If you already have Rodel open, click on Help and then About Rodel.

 

Why are some items in the Rodel window missing or appear to be offscreen?

This issue has been addressed in v1.96. If you are using an older version, try changing the resolution settings on your computer to resolve the issue. This is usually found in the Properties or Display settings area of your computer. A resolution of 1650 x 1050 normally works. Also, it's possible you may have the display set with Large Fonts (120 dpi) rather than Normal Size (96 dpi).

Can Rodel analyze more than 4 legs?

Yes. Up to 6 legs.

How do I change from left-hand drive to right-hand drive?

The right-hand/left-hand is selected when you open a "new" project (File > New). You cannot toggle between left-hand and right-hand after the project is started.

Can Rodel do operational analysis on turbo roundabouts?

Yes. With Rodel's geometric inputs, each entry is modeled for the specific geometry; therefore, it doesn't matter if it is a turbo or not.

How do I change print settings in Rodel?

Please watch this brief tutorial video.

Queue Distance

Are the 95th percentile queue lengths reported representative of the total queue distance? For example, we have a double-lane roundabout approach for which we got a reported 95th percentile queue length of about 25 vehicles. Does this mean the total queue distance is 25 vehicles (therefore a queue of 12.5 vehicles per lane) or that the queue is equal to 25 vehicles per lane?

Yes. The total queue distance is 25 vehicles; therefore it is a queue of 12.5 vehicles per lane.

Ramp Terminals

I am trying to run a capacity analysis on a roundabout where one of the legs has no exit lane. It's a freeway off-ramp coming into the roundabout, but Rodel is giving errors that it must have an exit width of at least one lane and a exit road width of at least one lane. How can you run an analysis on roundabout with a leg that just has entry lanes and no exit lanes such as a freeway off-ramp as mention above?

This is common at ramp terminals, with the off-ramp not having an exit lane and the on-ramp not having an entry. It is identified in Rodel as a 4-leg roundabout. In this situation, for example, the traffic distribution is such that no traffic is assigned to the exit side of the off-ramp and the entry side of the on-ramp. The specific exit geometry is not a factor in the analysis but is simply a placeholder for these essentially one-way streets (on-ramp, off-ramp).

Is the following statement contained in the Rodel 1 User Manual Issue 1.00 (p. 33) still valid? "It was found that the maximum RFC of 0.85 is often a quite misleading indicator of junction performance respecting queues and delays. (queues and delays themselves are much better indicators)."

Yes.

Can you please provide some additional information regarding the differences between the Peak 15 and Peak 60 results reported in the software? How is the delay calculated for both those periods? Can you provide the equation used to calculate delay?

In simplest terms, yes, they give different results because the Delay is being averaged over just the 15 peak with the 15-minute analysis (as per HCM methods) versus averaging over the entire 60-minute time period. Please review the User Guide (specifically the Arrival Flow and Traffic Flow sections) for further information and explanation.

Difference Between Rodel and HCM Models

I am wondering about difference between using Rodel Win and HCM models for roundabout capacity analysis. What do you recommend for U.S. conditions and do you have any comparison material you could share?

Rodel's capacity predictions show very strong correlation with recent FHWA capacity data collected on saturated roundabouts in 2012.

Rodel equations utilize "Time Dependent Queuing Theory," developed by U.S. researcher P.M. Morse, which is consistent with HCM methodology. Since delay is derived from the queuing theory equations, nothing in this respect is different from HCM to Rodel.

The significant difference is that Rodel incorporates a high definition queuing theory that, unlike HCS equations, allows for stable and accurate Delay and Q predictions even with higher v/c ratios (up to and exceeding 1.0). Moreover, it is a dynamic program as it ties all legs together, again unlike HCS 2010 in which each leg is analyzed separately. Rodel includes the HCM capacity model, which allows for easy comparison.

For more, please see our Basis and Validation & Transferability tutorials.

Control Delay vs. Queuing Delay

I am curious about the methods used to determine control delay versus queue delay. Specifically, if either method includes geometric delay and how this would impact the methods used for determining delay, whether control or queuing.

The HCM defines control delay as "the delay brought about by the presence of a traffic control device. Control delay includes delay associated with vehicles slowing in advance of an intersection, the time spent stopped on an intersection approach, the time spent as vehicles move up in the queue, and the time needed for vehicles to accelerate to their desired speed."

The HCM also notes other types of delay including geometric delay: Delay caused by geometric features in which vehicles reduce speed in negotiating a system element (such as delay caused from negotiating a roundabout).

Rodel implements the analysis procedures for both Control and Geometric Delay consistent with the HCM.

The practical outcome of Geometric Delay is that it's the Control delay plus approximately 4-5 seconds of additional delay. Most jurisdictions have adopted comparing just the Control Delay since signal programs typically haven't also included geometric delay.