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Driver Expectations When Navigating Complex Interchanges

Project Information

Project ID: 
Project Status: 
Start Date: 
Wednesday, September 1, 2010
End Date: 
Thursday, September 13, 2012
FHWA Program: 
FHWA Subprogram: 
Safety Design and Operations
FHWA Topics: 
Safety--Transportation Safety Planning (TSP)
TRT Terms: 
Interchanges; Safety; Signs; Research; Human Factors; Design
FHWA Discipline: 
Design, Operations, Safety
TRB Subject Area: 
Highways, Research, Safety and Human Factors

Contact Information

First Name: 
Last Name: 
(202) 493-3990
Email Address: 
Human Factors Team
Office of Safety Research and Development
Office Code: 

Project Details

Project Description: 

Multiple focus groups were presented with various signing and then asked to interpret the signing. They were also asked to decide if they were in a certain travel lane, en route to a certain destination, would a lane change be required.


The key project objective is to better understand driver expectations as they approach complex interchanges based on signing. 

Project Findings: 

Drivers expect that there will be functional relationships between lanes on the roadway and arrows/text on signs, and that the signs will make these relationships clear. Drivers expect that the distance between a guide sign and a "last chance" decision point will be sufficient to allow for making any necessary lane changes in a safe and timely manner. Drivers expect that they will have more than one opportunity to obtain necessary destination and lane information before they need to make a final decision regarding lane choices. Drivers expect that the freeway system—lanes, arrows and text on signs, lane markings, etc.—will provide them with the necessary information to construct a mental model and that it will be sufficient to support timely and accurate decisions about lane choice. Drivers expect that the information available to them through the freeway system will be sufficient to support decisions about lane choices; at the least, they will never have to move over more than one lane at the last moment. Drivers expect that the freeway system will provide sufficient information to support decisions about all route choices, not just frequent or popular choices.


Deliverable Name: 
Driver Expectations When Navigating Complex
Deliverable Type: 
Research report or guidelines
Deliverable Description: 
Interchange navigation presents a range of challenges that are different from those associated with driving on continuous roads. For example, interchanges force drivers to make time-sensitive task demands (i.e., forced-paced tasks). More specifically, drivers at unfamiliar interchanges must read the available signage, observe pavement markings, and determine a path through the interchange before they reach the gore point. Additionally, driver errors at interchanges are often more difficult to correct since drivers may transfer to a grade-separated freeway, highway, or roadway that provides limited access points to return to the original roadway. Clear navigation signage is needed to guide drivers and reduce errors. Although there has been previous research performed on signage in general, research specifically on interchange signage has been limited. There is little consensus on a best way to design signs for interchanges, and, in general, the current data on sign design is incomplete. The objective of this project was to begin addressing these information needs. This project yielded several overall conclusions related to driver expectations at complex interchanges. Namely, most drivers have problems at complex unfamiliar interchanges and feel stressed when they are surprised, are required to perform multiple lane changes in a short distance, or do not receive the information they expect. Several recommendations for sign designs are offered to help address these conditions. This report will be useful to traffic-safety researchers and traffic engineers responsible for highway design and public safety.