Musculoskeletal Function and Improving Intersections

People may move more slowly with age. Some older adults experience loss of limb strength, flexibility, sensitivity, and/or range of motion, or reduced ability to rotate the head and neck. Such changes may be the result of simple joint inflammation and deterioration (arthritis), muscle atrophy or paralysis related to stroke, or other problems. Chronic illnesses, such as coronary artery disease, heart failure and emphysema can greatly restrict and slow physical activity and mobility. General flexibility and head movements in particular are necessary to physically operate a motor vehicle, particularly for merging, lane positioning, and parking.

Reduced flexibility can affect a variety of driving tasks, especially where drivers have to visually scan a wide portion of the roadway environment. Some types of scanning cannot be eliminated, such as looking for other cars, pedestrians, or traffic signals, but it is important to avoid creating situations where excessive scanning is necessary. For example, consider skewed intersections where two roads meet at an angle that is less than 60 degrees instead of at a right angle. Because of their design, skewed intersections require more head movement and scanning. New highway projects should avoid skewed designs where possible. If a skewed intersection cannot be avoided, right turn on red should be prohibited because some older drivers will have a harder time detecting safe gaps in traffic.

The effects of age- and illness-related changes in flexibility on navigating skewed intersections are apparent. But physical difficulties may not seem relevant to providing advance guide and street signs. Advance information enables older drivers to ready themselves to make the appropriate responses, such as braking or turning. That small amount of extra time can make a difference. Advance signing enables drivers to focus on making a safe turn instead of having to look for a street sign at the same time.

Many older drivers like this motorist may experience reduced range of motion, making it harder to rotate the head and neck and therefore more difficult to navigate skewed intersections