Technical Resources

Geometric Design Resources

The following is a listing of the most recent publications for this topic.

PUBLICATION TITLE
Factors Influencing Crash Severity at Rural Horizontal Curves in Maine
According to the Federal Highway Administration (FHWA), in 2008 nearly one-fourth of the fatalities occurred at horizontal curves. Particularly, fatality rates at rural horizontal curves are more than twice than that at urban horizontal curves. Fatal-and-injury (FI) (i.e., incapacitating injury crash, non-incapacitating crash, and possible injury crash) crashes accommodate roughly half the number of total crashes. Hence, addressing the safety problem at horizontal curves is one of FHWA's three focus areas. The Strategic Highway Safety Plan prepared by the American Association of State Highway and Transportation Officials (AASHTO) also counts crashes at horizontal curves as one of 22 emphasis areas.
May 1, 2019
Safety Effect of Smart Right-turn Design at Intersections
Intersections are recognized as the most hazardous locations on roads since conflict possibilities are high at intersections. This often results in a high frequency of fatal and severe crashes at intersections. Although intersections constitute only a small proportion of the entire roadway system, a significantly high proportion of crashes are reported at intersections. More than 50 percent of the combined fatal and injury crashes occur at or near intersections. More than 9,000 people lose their lives in intersection crashes every year in United States. Many of these fatal and severe intersection crashes are reported at right-turns and are predominantly attributed to wide angle, sweeping, high-speed, right-turns.
Nov 1, 2018
A New Interchange Design: The Double Offset-T Interchange
Transportation engineers are facing great challenges in meeting the mobility demands of an increasing population. As traffic demands continue to rise at many highway junctions, motorists, pedestrians, and bicyclists all experience longer delays and greater safety risks. Today's traffic problems are very complicated, and conventional intersection designs are often found to be insufficient to alleviate them. As a result, various innovative intersection designs are being investigated and implemented to mitigate or solve these complex problems.
Oct 2, 2018
Mini-roundabouts in Minnesota Benefits of Roundabouts with a Smaller Footprint and Lower Cost
The Minnesota Department of Transportation (MnDOT), cities, counties, and the consultant community have made great strides in utilizing a broader range of intersection types to solve transportation problems in Minnesota. By the end of the 2018 construction season, MnDOT and local agencies will have constructed 29 restricted crossing U-turn (RCUT) intersections, six diverging diamond interchanges (DDI), two continuous Green T intersections, and more than 100 roundabouts.
Aug 1, 2018
Urban Street Geometric Design Handbook - Errata
Urban Street Geometric Design Handbook - Errata
May 14, 2018
Implementing Context Sensitive Design Handbook
Published in 2017, this new informational report includes an expanded focus on topic areas such as freight accommodations, speed management, and context sensitive design in lower density urban and built-up suburban environments. A number of real-world case studies are also included in the report, to demonstrate the medium- and long-term impacts of successful context sensitive design projects.
Nov 1, 2017
Protected Bikeways Practitioners Guide
This guide provides an easy-to-navigate document for planning, designing, operating, and implementing protected bikeways in the United States and Canada. The Guide provides references to the critical design standards and guidelines in these two countries that direct the geometric and operational design of protected bikeways, including international best practices and research, and fills current gaps in guidance based on best practice examples.
Jul 1, 2017
Guide for Geometric Design of Transit Facilities
This AASHTO guide provides a comprehensive reference of current practice in the geometric design of transit facilities on streets and highways, including local buses, express buses, and bus rapid transit operating in mixed traffic, bus lanes, and high-occupancy vehicle lanes, as well as bus-only roads within street and freeway environments. It also covers streetcars and LRT running in mixed traffic and transit lanes, and within medians along arterial roadways. These guidelines are based on a review of relevant AASHTO, TRB, and ITE documents, as well as design reports provided by various transit agencies. They are designed for use by public agencies, practitioners, and developers in need of basic information about planning, locating, sizing, designing, and implementing transit facilities along roadways.
Aug 1, 2014
Evaluation of Light Rail Transit (LRT) in Downtown Houston
As part of the METRO Solutions program, we evaluated the impact of three Light Rail Transit (LRT) lines on traffic operations in downtown Houston. We modeled the interactions of automobile and bus traffic with three LRT lines (Red Line, East End Line, and Southeast Line). We performed traffic projections to approximate future year traffic demands, applied a trip reduction factor to account for the Downtown transit facilities, and analyzed AM and PM peak hours for future year conditions for the with interline and without interline scenarios. In the with interline scenario, the East End trains merge onto the Red Line alignment to reach the intermodal terminal while Southeast trains continue all the way to the western terminus. In the without interline scenario both East End and Southeast trains travel to the western terminus. Some of the key factors identified in this analysis to efficiently operate the LRT system include train control system, signaling coordination, effective geometric design, increasing driver awareness, effective signal timing, effective driveway control, effective signage, preemption locations, and integration between the traffic signal system and the train signal system. We recommended deploying a train control system that would modulate station dwell times as a means of continuously optimizing train headways on each of the three routes that pass through the study area. This also minimizes clustering of trains and degradation of intersection level of service. Our traffic models and analysis have served as useful tools for stakeholders to further understand the impact of the downtown LRT system.
Aug 1, 2012
A Policy on Geometric Design of Highways and Streets, 6th Ed
AASHTO's bestselling publication, A Policy on Geometric Design of Highways and Streets, 6th Edition, 2011, also known as the "Green Book," is now available. This publication contains the current design research and practices for highway and street geometric design and provides guidance to highway engineers and designers who strive to make unique design solutions that meet the needs of highway users while maintaining the integrity of the environment. It is also intended as a comprehensive reference manual to assist in administrative, planning, and educational efforts pertaining to design formulation. Design guidelines are included for freeways, arterials, collectors, and local roads, in both urban and rural locations, paralleling the functional classification used in highway planning. The book is also organized into the following chapters to stress the relationship between highway design and function: Highway Functions, Design Controls and Criteria, Elements of Design, Cross-Section Elements, Local Roads and Streets, Collector Roads and Streets, Rural and Urban Arterials, Freeways, Intersections, and Grade Separations and Interchanges.
Dec 1, 2011
Developing a Corridor System Management Plan for I-215, CA
The I-215 Corridor System Management Plan for Caltrans is aimed at improving mobility on I-215 in the Riverside and San Bernardino Counties in California. We are assessing corridor-wide performance of 44 miles of I-215 with several interacting bottlenecks, 3 major system interchanges, 35 service interchanges, HOV lanes and multiple ramp meter locations. As part of the data needs assessment, we used an extensive data collection plan. We conducted turning movement counts at all the signalized intersections and strategically-located freeway mainlane counts. We visited every study intersection, performed field reconnaissance, noted lane utilizations, spillbacks, and bottlenecks for each peak period. We also identified the bottlenecks causes such as lane drops, merging freeways, weaving, hilly terrain, land use, geometric design, etc. We collected travel time runs using the floating car technique and GPS systems. We also developed existing conditions models with adaptive ramp metering using the VISSIM® traffic simulation program. We calibrated our model using counts and travel time runs to reflect existing traffic conditions. We are validating our model using queue lengths for four hours each of AM and PM peak periods. Based on our assessment of density, speed, travel time, delay, and level of service, we are recommending corridor management strategies to improve mobility along I-215. We will develop and analyze future models and evaluate the impact of managed lanes, auxiliary lanes, ramps, multimodal considerations and other improvements. This will help us prioritize the corridor needs and develop a phased implementation of improvements.
Aug 1, 2010
Enhancing Intersection Safety Through Roundabouts
Enhancing Intersection Safety Through Roundabouts is an Informational Report of the Institute of Transportation Engineers (ITE). The goal of this report is to promote the safety benefits of modern roundabouts by providing a synthesis of available research, including international experience. The report also includes a summary of available information regarding geometric design features, traffic control devices, lighting and landscaping elements to further enhance safety at roundabouts. This report reflects the current knowledge base, which will of course change over time as practitioners and researchers gain further insight into the safety aspects of roundabouts.
Dec 1, 2008
Urban Street Geometric Design Handbook
This Handbook provides comprehensive, practice-oriented guidance that focuses on the operational and safety aspects specifically related to the geometric design of all classifications of urban surface streets (local streets, collector streets, arterial streets and their intersections). It identifies techniques, procedures and guidelines that have been applied to a wide variety of newly constructed or reconstructed street projects. The handbook recognizes the range of transportation modes and the integration of vehicles, pedestrians and bicycles for urban roadways.
Dec 1, 2008
Urban Street Geometric Design Handbook Index
Urban Street Geometric Design Handbook Index
Dec 1, 2008
Urban Street Geometric Design Handbook Table of Index
Urban Street Geometric Design Handbook Table of Index
Dec 1, 2008
ITE Handbook Summary A New Geometric Design Handbook for Urban Street
ITE Handbook Summary A New Geometric Design Handbook for Urban Street
Oct 1, 2008
A Simplified Roundabout Design Method
This paper discusses a simplified process for designing roundabouts. In Australia, the development of the design processes for roundabout design came through the application of fundamental principles of geometric design, which were then modified in the early 1980’s to reflect the latest research from the UK -- in particular the influences of geometry on safety.
Mar 1, 2008
Urban Street Geometric Design Handbook Errata
Urban Street Geometric Design Handbook Errata
Jan 1, 2008
ITE Report Summary Guidelines for the Design and Application of Speed Humps:An ITE Proposed Recommended Practice
This report provides updated state-of-the-practice guidance for the design and application of speed humps, one of several geometric design techniques to control vehicular traffic speeds along a roadway.
Sep 1, 2007
Operational Analysis of Proposed Roundabouts in Gorham, Maine
The Maine Department of Transportation is proposing to construct three new roundabouts as part of the Gorham Bypass project. The project is currently in the design stage. An operational analysis of the design year traffic was conducted early in the project development stage for two of the three roundabouts. This operational analysis at the early conceptual design stage was used to guide the developing design. The analysis helped the designer determine the need for certain geometric design elements, such as if multilane approaches were needed and if right-turn bypass lanes were appropriate. This paper describes the simple procedure used and the benefits gained by performing a planning level analysis at an early phase in project development prior to commencing with detailed design. The operational analysis also compared three methods for estimating the approach capacities; 1) procedure from the FHWA Roundabouts: An Informational Guide (based on simplified British regression model); 2) procedure from the Highway Capacity Manual (HCM) 2000 (using the conservative lower bound value); and 3) the recommended model from the NCHRP Project 3-65 (results published in NCHRP Report 572: Roundabouts in the United States). The models suggested from NCHRP Project 3-65 will likely be adopted for inclusion in a future edition of the Highway Capacity Manual. For each roundabout approach analyzed, the NCHRP Project 3-65 recommended model produced the lower, or more conservative, value of the approach capacity. The differences in the computed approach capacities from the NCHRP 3-65 model compared to the HCM 2000 model were significant enough to influence key geometric design choices. Where the HCM 2000 procedure showed all single lane approaches to operate acceptably, using the NCHRP 3-65 model suggested a possible need for some multilane approaches and possible right-turn bypass lanes. This paper describes the operational analysis methods used and how the results directly influenced important geometric elements in the roundabout designs.
Aug 1, 2007