History

Rodel developer Barry Crown's depth of knowledge and breadth of experience with modern roundabouts is without parallel. Since 1977, Mr. Crown has designed, evaluated, redesigned, modified, and audited over 1,000 modern roundabout and mini-roundabout installations. These include high capacity US roundabouts for volumes up to 7,500 Vehicles Per Hour (VPH) on roadways carrying up to 80,000 Average Daily Traffic (ADT).

Mr. Crown was asked to serve as advisor on the first FHWA Roundabout Guide, and for the 2010 revision of that document (NCHRP 672). He has instructed numerous roundabout design courses for state, provincial, and local governments in the US, Canada, and UK. Over the years, he has encountered design problems we have yet to experience, and answered questions that most of us haven't yet thought to ask.

Barry programmed the roundabout capacity software that made his achievements possible. Now, due to numerous requests, he has poured his years of experience into Rodel and made the program available in a Windows format for other practitioners.

Barry's original idea for Rodel emerged in the 1980s, to accommodate the different needs and perspectives of transportation planners and design engineers.

The design task typically begins with the designer requesting forecast traffic. Then, to forecast the traffic, the planner needs to know the delay at the proposed roundabout. Without knowing the geometry, the planner has to assume the delays, so the initial traffic forecast is a rough guess that can only be refined when the designer provides the geometry and delays. If those are consistent with the original assumption, there's no need to revise anything and the job is done. But if not, the forecast has to be redone, and the design has to be modified - perhaps several more times. In ancient times (1983), that was a drawn out, time consuming process.

Rodel was conceived to overcome that problem by drastically shortening design time. This enabled better coordination between planning and design staff, and allowed each to rapidly modify their proposals and reach consensus. Since the time and effort required for design is now shortened, revised traffic forecasts based on the latest geometry are far more acceptable to the design engineer.

The side effect of fast design speed is that it allows the designer to explore many alternative roundabout geometries in a very short time, and thus create more optimal designs with robust capacity performance and superior safety. In short, Rodel allows better roundabout design.

By popular request from practitioners in the US, Canada, and the UK, Mr. Crown has upgraded Rodel to operate on a modern Windows platform and added features to accommodate modern design issues and system evaluation requirements.

If you've tried other capacity programs, we are sure you will appreciate Rodel's speed and accuracy, the design confidence derived from field measured capacity and robust statistical parameters, and the versatility of Rodel's new output features.