PUBLICATION NO. FHWA-NHI- FHWA-NHI- Innovative Intersections and Interchanges Participant Notebook Intentionally Blank Innovative Intersections and Interchanges Participant Notebook INTRODUCTION Thank you for choosing to participate in this training workshop on innovative intersections and interchanges offered through the National Highway Institute (NHI). In the United States, over the last several years an average of one-quarter of traffic fatalities and roughly half of all traffic injuries occur at, or near, intersections. In addition to being a substantial safety challenge, intersections may also become very congested when traffic volumes are high, resulting in user delay and frustration that ultimately may compound into larger regional mobility problems. Motorists, pedestrians, and bicyclists face greater mobility challenges and safety risks at intersections as traffic volumes grow and congestion worsens. Agencies need safer, more balanced designs that keep people moving. Innovative intersection designs offer many safety and operational benefits, and are being built more often because they can deliver more for less. The Federal Highway Administration (FHWA) launched the Every Day Counts (EDC) state-based initiative to identify and rapidly deploy proven but underutilized innovations aimed at reducing project delivery time, enhancing roadway safety, reducing congestion, and improving environmental sustainability. In 2012, Intersection & Interchange Geometrics (IIG) was selected as a featured innovative technology in EDC Round-2. IIG consists of a family of innovative intersection designs that improve intersection safety while also reducing delay, and at lower cost and with fewer impacts than comparable traditional solutions. In continuing effort to advance the deployment of innovative intersection designs, FHWA is pleased to offer this training workshop to assist transportation professionals in better understanding these intersections and the potential benefits they can provide when correctly implemented. For further information or to offer comments on this training material, please contact: Mark Doctor - FHWA Resource Center: [email protected] Jeff Shaw – FHWA Office of Safety: [email protected] TARGET AUDIENCE The target audience for this training includes state and local transportation agency personnel, and/or consultants having responsibilities for developing and designing elements pertaining to intersections and interchanges. 1 Innovative Intersections and Interchanges Participant Notebook GOALS AND OUTCOMES The overall course goal is to make design engineers aware of new intersection and interchange designs that improve traffic operations and safety at a much lower cost than most other viable alternatives. Specifically, participants should be able to perform the following after attending this course: • Describe the principal features of the innovative geometric designs presented including key design and operational features • List the advantages and disadvantages of their use • Assess what innovative designs would be applicable at a given location given the conditions and constraints • Identify resources to acquire additional information on these designs and their implementations COURSE CONTENT Module 1: Introduction – This session includes a brief overview of common intersection problems that agencies are trying to solve and introduce the concepts of intersection conflict points to understand safety issues and phasing issues at signalized intersections. Module 2: Restricted Crossing U-Turn (RCUT) – Also known as J-turns, superstreets, and reduced conflict intersections, this module describes the features, safety advantages and potential applications of the RCUT. Module 3: Median U-Turns (MUT) and Other Indirect Left Turns – Focuses on the features of the MUT as well as other indirect left turn intersections with similar features. Module 4: Displaced Left Turn Intersection (DLT) – Commonly referred to as the Continuous Flow Intersection (CFI), this module will concentrate on the DLT features and benefits. Module 5: Continuous Green-T Intersections – A short discussion on this design for three-leg intersections and their applicability. Module 6: Diverging Diamond Interchange (DDI) – A comprehensive discussion of the features and benefits of the DDI will be explored. Module 7: Assessment and Evaluation Process – Describes the advantages of utilizing a formal intersection / interchange evaluation process to determine which geometric solution might work best at any given location. 2 Innovative Intersections and Interchanges Participant Notebook Module 1: Welcome and Introduction Meet Your Instructor(s): Mark Doctor, PE Jeffrey Shaw, PE FHWA Resource Center FHWA Office of Safety [email protected] [email protected] 404-562-3732 708-283-3524 Participant Introductions: . Your name . Your Agency/Organization . What would you like to learn from this workshop? Logistics: . Please silence cell phone devices . Please ask questions . Schedule o Breaks o Lunch . Restrooms/Emergency exits . Sign-in sheet and registration form Source: Google Images MODULE 1 LEARNING OUTCOMES Define “intersection conflict points” Describe the “Safe Systems” concept as potentially applied to intersections List the common characteristics of “innovative” or “alternative” intersections and interchanges 3 Innovative Intersections and Interchanges Participant Notebook WHY INNOVATIVE INTERSECTIONS & INTERCHANGES? Which of these intersection problems/challenges do you face? • Increasing Congestion • Too Many Crashes • Mobility for all modes (Bicycles, Pedestrians, Transit) • Not Enough Funding • Time Consuming Projects • Inability for more right-of-way • Impacts of projects (Environmental, social, economic) INTERSECTION SAFETY FACTS Intersections are usually bottlenecks along high-volume roadways and are often a safety concern. With Intersections: BIGGER is not always BETTER 4 Innovative Intersections and Interchanges Participant Notebook Important Safety Facts: Statistics show that about half of all severe crashes occur at an intersection. Angle crashes account for over 40% of fatal crashes at intersections Left-turn crashes account for over 20% of fatal crashes at intersections Ped & Bike crashes account for 25% of fatal crashes at signalized intersections 5 Innovative Intersections and Interchanges Participant Notebook INTERSECTION CONFLICT POINTS Intersections are inherently locations for users crossing paths (i.e. conflict points). If users make incorrect judgements or disobey traffic control devices, those conflicts could result in a collision. Assuming single lane approaches, a typical 4-leg intersection has 32 conflict points among vehicles. Breaking down the 32 conflict points: . 16 crossing conflict points (most critical) . 16 merging/diverging conflict points Source: FHWA’s Signalized Informational Guide – Exhibit 4-3(b) Every vehicle conflict point is affected either directly or indirectly by left-turn movements There are four vehicle-pedestrian conflicts per crossing. Conflicts involving right turn on red and “permissive” left-turns can be particularly problematic. 6 Innovative Intersections and Interchanges Participant Notebook SAFE SYSTEMS APPROACH “Safe System is the management and design of the road system such that impact energy on the human body is firstly avoided or secondly managed at tolerable levels by manipulating speed, mass and crash angles to reduce crash injury severity.” Source: Austroads Report AP-R560-18 Towards Safe System Infrastructure: A Compendium of Current Knowledge Basic Principles: • There is shared responsibility for safety among the Human, the Vehicle, and the Infrastructure that works together to minimize harm. • Recognition and acceptance that crashes will occur due to human error, but seek to reduce systemic opportunities for errors to occur. • When crashes do occur, manage their energy so that the outcomes are not severe. Firstly – try to avoid the crash!!! Simplify Driver Decisions and Clarify with Positive Guidance . Human Factors Guidelines . Reduce the potential for a collision . Intersection Conflict Points Manage Speed – higher speeds equate to longer distances to react and brake Modest reductions in travel speed approaching intersections can produce quite large reductions in the risk of deaths and serious injuries. When a conflict happens at slower speeds, a driver travels a shorter distance in the time required to react, increasing the opportunity to either avoid a collision or reduce the speed upon impact. Once the brakes are applied the stopping distance increases with the square of the initial speed. 7 Innovative Intersections and Interchanges Participant Notebook Even if a vehicle can’t stop completely before impact, a modest reduction in approach speed makes for a much greater difference in the speed on impact. View an exceptional public service announcement developed in Australia: https://www.youtube.com/watch?v=ZfdbeecfiJo The human body’s tolerance to the physical force of being in a crash is at the center of a Safe System approach to considering safety. Applying a Safe System approach to intersections requires an understanding of the relationship between speeds and angle of impact (the inescapable laws of physics) to determine how much force (kinetic energy) the human body experiences in the event of a crash. Reducing the overall kinetic energy of the impact can increase the odds for it to be survivable. The figure below is from Australian research conducted on the effects of