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 Critical objects or conditions

By Chuck Huss, C.O.M.S.

Drivers, especially those who are visually challenged, need to be constantly aware of critical objects or conditions present within their ever-changing driving environment.

The following document is intended to provide readers with a brief overview of : critical objects/conditions as pertinent to the driving task; the importance of their early detection and identification; and examples of the three (3) major groups of critical objects or conditions.


A critical object or condition is defined as any object or condition which can be predicted to cause drivers to modify their vehicle's speed, lane position or planned path of travel.

Importance in detection and identification:

Experts stress that all drivers learn how to group these objects or conditions into three general categories: roadway characteristics, roadway users and traffic control devices.

Grouping facilitates object recognition and decision making, affording drivers an increased margin of safety to decrease hazard or decrease the likelihood of collision in their dynamic driving environment *.

Integrating the latter grouping concepts with other defensive driving and hazard perception skills is also one of the ways in which drivers can compensate for the driving errors of others.

For example, incorporating ample eye lead time and head and eye scanning skills into the driving task, helps assure that you will have sufficient time and distance to decide whether or not to react to hazards present within, along side of or approaching your path of travel. Eye lead time simply refers to where your vehicle will be in the next so many seconds of travel time …. the greater the driver's speed, the further out ahead you have to look to detect and identify critical objects or conditions in time; in order to stop if necessary or react accordingly with adjustments in speed, lane position or both.

Likewise, illustrating a 3 - 4 second following distance from other road users, leaving yourself an out for collision avoidance purposes and the use of turn signals, horn and headlights to apprise other road users of your presence or intentions will increase the probability several-fold that you will reach your intended objective and return home safely.

Examples of the three general categories of critical objects/conditions:

  • Roadway Characteristics: 

· Roadway itself - presence or absence of a road shoulder - number of lanes - cement or other medians/abutments - curves, dips, hills, slants/tilts, camber 

· Intersections 

· Fixed hazards within, alongside of or near the roadway inhibiting sight distance of drivers such as: - shrubs - hedges - gradient of the land - hillsides - trees - road signs - telephone or utility poles - traffic control boxes - commercial signs - narrow bridge - tunnel - low clearance areas

  • Roadway Users: · Anyone or anything on 2 feet or 4 feet · Anyone or anything on 2 or more wheels
  • Traffic Control Devices: · Pavement markings · Traffic lights · Crosswalk lights · Road signs - regulatory - warning - guide - services - construction - recreation · School guard · Law officer · Construction markings - barrels - cones - flag person - portable signs/digital displays

* Taken from Huss, C.P., (1988). Model Approach - Low Vision Driver's Training and Assessment. Journal of Vision Rehabilitation, Vol. 2, No.2, pp. 31-44.


Charles P. Huss, C.O.M.S. Coordinator, Low Vision Driver Services

West Virginia Rehabilitation Center P.O. Box 1004 Barron Drive Institute, WV 25112 TEL: 304-766-4803 FAX: 304-766-4816  Charles P. Huss is an Academy Certified Orientation and Mobility Specialist with 25 years of teaching experience with visually impaired individuals [K-Geriatrics].




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