Human Factors Guidelines for Road Systems: Second Edition (2012) / Chapter Skim
Currently Skimming:
Pages 46-58
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 46... ...
Task Analysis of Curve Driving .
|
From page 47... ...
HFG CURVES (HORIZONTAL ALIGNMENT) Version 2.0 6-2 TASK ANALYSIS OF CURVE DRIVING Introduction This guideline identifies the basic activities that drivers would ty pically perform while trying to safely navigate a single ho rizontal curve.
|
From page 48... ...
Discussion The information about driving tasks in the previous page is taken from the task analysis described in Tutorial 3 that breaks down curve driving into its perceptual, cognitive, and psychomotor components. A key concept for understanding the curve driving task is the visual and vehicle-control demand, which refers to the amount of time that drivers are required to focus their attention on curve driving activities, such as acquisition of visual information and maintaining vehicle control, to the exclusion of other activities they could otherwise be doing while driving (e.g., scanning for hazards, viewing scenery, changing the radio station, etc.)
|
From page 49... ...
Ac ce pta ble Ra ng e Ac ce pta ble Ra ng e HFG CURVES (HORIZONTAL ALIGNMENT) Version 2.0 THE INFLUENCE OF PERCEPTUAL FACTORS ON CURVE DRIVING Introduction The perceptual factors in curve driving refer to the driver's use of visual information to assess the curvature of an upcoming curve.
|
From page 50... ...
Discussion Curve perception is an im portant part of curve driving because, in the absence of extensive experience with a curve, drivers mu st rely on their judgm ents about a curve to select a safe speed for curve entry. Speed signage inform ation can assist drivers; however, evidence suggests that this inform ation is not a prim ary source for speed selection in curves ( 1 )
|
From page 51... ...
SPEED SELECTION ON HORIZONTAL CURVES Introduction Various sources attem pt to exam ine speed data for roadway geom etry and to deter mi ne desirable speeds for horizontal curves. AASHTO policy defines design speed as "a selected speed used to de termine the various geometric design features of the roadway" ( 1 )
|
From page 52... ...
Discussion Drivers' failure to accurately judge the appropriate driving speed on horizontal curves can have safety consequences. The Fatality Analysis Reporting System (FARS)
|
From page 53... ...
C OUNTERMEASURES FOR I MPROVING S TEERING AND V EHICLE C ONTROL T HROUGH C URVES Introduction Successful navigation of curves depends on accurate steering and speed cont rol in order to mi ni mi ze lateral acceleration within the lane. Design of alignm ents that c onform to driver expectations and typical behaviors will enhance the driver's ability to control the vehicle.
|
From page 54... ...
Discussion The steering control task has been m odeled as a two-level process com posed of an open-loop anticipatory com ponent (far view) for predicting curvature and steering angle, and a closed-loop com pensatory com ponent (near view)
|
From page 55... ...
COUNTERMEASURES TO IMPROVE PAVEMENT DELINEATION Introduction This guideline describes countermeasures that support improvements in curve detection and driver performance through the use of pavement surface markings, such as edge lines, raised retroreflective pavement markers (RRPM) , transverse stripes, etc.
|
From page 56... ...
Discussion Road delineations provide cues that assist drivers in detecting curves and assessing the level of curvature. Road surface markings provide the strongest curvature cues and are best for providing short-range steering control cues (compensatory control -- see "Countermeasures for Improving Steering and Vehicle Control Through Curves")
|
From page 57... ...
S IGNS ON H ORIZ ONTAL C URVES Introduction Prior to a change in the horizontal alignm ent of a roadway, inform ation about this change should be conveyed to drivers via roadway signs. This inform ation should be co mm unicated in a concise and efficient ma nner such that drivers have tim e to process the information and adjust their speed as well as alter the vehicle path appropriately.
|
From page 58... ...
Discussion Numerous studies have shown the effectiveness of advanced warning signs for curves (2, 3, 4, 5)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.