Shining a Light on Intersection Safety
A Photorealistic Approach to Intersection Safety
Diverging Diamond Interchange in Orlando, FL
The I-4 “Beyond the Ultimate” program is one of Florida’s most ambitious highway improvement initiatives. I-4 BTU is a program to add toll-accessed median express lanes to over 40 miles of Interstate 4 in the greater Orlando area. Recently, RDV Systems was asked to assist the BTU engineers in assessing the safety of a lighting scheme for one of the project’s major interchanges. The task was particularly challenging, as it required applying RDV’s photorealistic 3D visualization technology to create an accurate model of nighttime conditions under various lighting scenarios. RDV rose to the challenge and exceeded expectations.
The City of Orlando attracts over 75 million visitors every year and is home to some of the world’s most loved and finely manicured theme parks. Aesthetics are important to the City, and the interchange in question serves as a primary link between popular hotel complexes, the Orlando Convention Center, and Walt Disney World, Universal Studios, and Sea World theme parks, among many others. With such a massive number of visitors expected to use the interchange on a regular basis, the City of Orlando sought to enhance the interchange’s visual appeal by placing several ultra-modern illuminated pylons on both sides of the highway adjacent to the interchange.
Here’s what the BTU Communications Manager, Chris Patton from Global-5 Communications had to say: “The interchange is used by a great many visitors to all of the nearby attractions. The architects and engineers came up with a stunning, futuristic nighttime lighting solution for the interchange, but it raised concerns that decorative lighting features might impact drivers’ ability to see the traffic signals clearly”.
I-4 BTU – New Diverging Diamond Interchange
For the BTU project, the project team had decided to redesign the interchange into a diverging diamond configuration, or DDI. DDIs are relatively new to the US highway scene, but are gaining in popularity as they have been shown to increase capacity, reduce congestion, and most importantly, greatly improve driver safety (see below for more information on DDIs). Florida DOT introduced its first DDI in May 2017 and now has over 50 such configurations in use or in the works throughout the state.
Blinded by the Light
As the project team reviewed the city’s proposal, the DOT and consultant safety engineers became concerned that having such large, bright light sources near the intersection would make it easy for drivers to miss seeing the traffic signals at night, thereby creating a significant safety hazard.
The issue then became how to accurately evaluate the effects of the pylon lighting on traffic light visibility. The engineers also wanted to determine if changes in the orientation of the pylons or the colors of the lighting would make a difference. There was no reliable way of evaluating the effects on visibility for these scenarios using traditional safety engineering methods.
Modeling with Leading-Edge Animation Tech
More specifically, RDV had recently added rapid, on-demand generation of highly photorealistic imagery to its software suite, and Global-5 asked if this could be used to simulate the actual driver’s-eye nighttime views at critical locations. RDV is no stranger to road safety applications. In addition to visualization modeling, RDV also provides the Road Safety Audit 3D (RSA 3D) technology, an application that uses highly accurate 3D models of existing and proposed highway infrastructure to perform safety simulations such as stopping and passing sight distances, intersection sight distances, and analysis for many other aspects of roadway safety.
RDV was already teamed with the project’s public involvement consultant Global-5 to provide 3D virtual models of the proposed interchange to facilitate public and stakeholder engagement activities. Having seen the power of RDV’s 3D visualizations first-hand, and with the 3D model of the interchange already built-in RDV’s systems, the project team turned to RDV once again to help with the pylon lighting conundrum.
“RDV had already provided us with a detailed 3D model of the interchange, and we had seen what they could do with realistic image generation. So we asked if they help the design team with their safety assessment.”
Matt Hamill, COO of Global 5
“This project presented a truly unique challenge”, said RDV’s CEO Natan Elsberg.
“We’ve done photo-realistic nighttime visualizations before, but those were primarily to show aesthetics. For this project It wasn’t enough to make great looking images – we had to realistically account for a range of different lighting characteristics from a variety of sources and the interplay between them, including light from the pylons, vehicle headlights, streetlights, traffic and pedestrian signals, reflective striping, and even the reflectivity of overhead signs.”
The project team selected two key interchange locations at intersection stop bars and asked for images that would show what drivers would actually see when using different pylon light colors (green or white) and both forward-facing and rear-facing pylon orientations. RDV got to work with its ray-tracing rendering engine to use the underlying 3D model to generate the requested images.
Click on Any Image to Enlarge
Greenlighting The Pylons
Ray tracing is the rendering technique used to create highly realistic imagery for video games, animated films, special effects, and visualization modeling. It uses a robust recursive algorithm to simulate the effects of both direct and ambient lighting, shadowing effects, and reflectivity and absorption characteristics of different surfaces.
To provide thelevel of realism needed for making the necessary safety engineering decisions, RDV engineers had to accurately define the actual lighting characteristics of the various light sources in great detail. These included incorporating IES (Illuminating Engineering Society) specifications such as the illumination intensity, shape, and distribution characteristics for each light source. Particularly challenging was modeling the retro-reflectivity of signs and roadway striping, i.e., how much light is reflected back to drivers by reflective paint on signs and striping.
Click on Any Image to Enlarge
The results of these efforts were several true-to-life and very telling images of how the selected locations would look with the proposed pylon lighting, in the different scenarios. The clarity and quality of the images were exactly what the consultant and the project teams’ safety engineers were looking for, as a basis for deciding which option to go with.
“The project team was very happy with the outcome of the RDV lighting model and analysis, The design process is still underway, but the safety engineers are now confident that they have the tools and assets needed to make the best possible decisions and recommendations”
Kevin Stewart, Director of Operations North America
RDV Systems Inc.
Making the Counter-intuitive Understandable
Diverging diamond interchanges, or DDIs, are an example of “innovative” roadway designs, which use new ways to solve old problems, but do not always make sense to the average driver at first glance. The use of DDIs worldwide is growing where limited access highways meet busy local roads.
In a diverging diamond Interchange, both directions of traffic on the non-freeway road flip to the opposite side of the road while traveling through the interchange, and then flip back to normal right-side traffic flow. This temporary switch in traffic direction means that vehicles can make left turns to enter or exit highway access ramps without having to cross oncoming traffic. Compared to a traditional diamond interchange, a DDI layout reduces the number of vehicle conflict points from ten locations to just two. Not only does this increase safety, but it reduces the number of traffic signal phases needed, resulting in higher traffic volume capacity.
While these advantages may be evident to roadway engineering professionals, conveying the benefits of DDI’s to other parties is no trivial matter, especially as their traffic side switching design can be counterintuitive. By bringing in RDV, Global-5 was able to overcome these obstacles and effectively convey the reasoning for choosing a DDI configuration to a variety of project stakeholders and the broader public.