Driver Information Overload
National Cooperative Highway Research Program (NCHRP) Project
3-50 produced a report (see below) and a computer program that provides
a means of analyzing driver information overload (DIO). Drawing
on the results of the project and previous research, the NCHRP determined
that, as a general rule, an individual guide sign is likely to cause
DIO for some drivers if it contains more than two destinations or
route symbols, especially if the word length exceeds seven letters.
Where multiple signs are on a sign structure, DIO can result
from any of the following:
- two sign panels with more than two destination names and two route symbols on any one sign
- three guide sign panels with any one sign having more than two destination names
- more than three sign panels, regardless of message content.
DIO is likely to occur at locations where information is dense
in terms of proximity of signs and sign message content. More specifically,
DIO is likely where spacing between two guide signs, including supplemental
signs, is less than 800 ft, where there is one destination on the
second sign, and 1200 ft where there are two or three destinations
on the second sign.
Report and Program Available.
The computer
program (CRP-CD-36) developed through NCHRP Project 3-50 is included
with the report when the report is ordered from the Transportation Research
Board. (Lerner, N.D., R.E. LLaneras, H.W. McGee, Sunil Taori, and
G. Alexander. Additional Investigations on Driver Information
Overload
, NCHRP Report 488, Transportation Research
Board, Washington, D.C., 20003)