All of us have walked on a sidewalk that was too narrow for the amount of pedestrian traffic.  Pedestrians typically are either forced to, or choose to, walk on the adjacent turfgrass when meeting others.  At the same time, we have also walked on a sidewalk that seems too wide.  Sidewalks that are “too wide” is an infrequent occurence, unless of course you enjoy walking the streets of New York City at 4:00 am.
I am reminded of the lack of sidewalk width each day as I walk my daughter to school.  The sidewalk directly in front of her school is 5-feet wide.  98% of each school day, 5-feet is an adequate width for two pedestrians to walk side by side on the sidewalk.  However, during the morning and afternoon rush, students walking with their parents frequently overflow on to the adjacent landscape

Landscape is a generous word for this because what it actually becomes is exposed earth where the existing turfgrass or plant material is trampled beyond life.

Cities and schools, with a few exceptions, can not afford the additional cost for widening a walkway, nor do they wish to spend their money on it.  However, the maintenance factor of re-seeding, replanting or cleaning up mud that has been tracked into the building is not typically considered in the cost equation.
One mitigation option is to increase the width of the sidewalk, in this case 10-feet is the appropriate width necessary for two people to meet two other people on the sidewalk.  However, increasing the width of the sidewalk has its complications, most notably the cost for additional concrete and increase in impervious surface.  Money for landscape improvements are usually the first cut from a budget and the least of concerns.
The mitigation method that I recommend is aligning the sides of the sidewalks with a compacted breeze or decomposed granite material.  The functional aspects of overflow pedestrian traffic can be met with an informal appearance in most instances.  Compacted breeze and decomposed granite provide a great porous ground plane material that is very pleasing to walk on, even for a female with high heels.  According to local Colorado Springs landscape contractor Matt Hiner of Hiner Landscapes, compacted breeze costs about half of the cost of concrete.

By adding compacted breeze or decomposed granite along the edge of a concrete sidewalk, the functional aspects of a wide sidewalk are provided without the extra cost and impervious surface.

In addition to increasing the width of sidewalks, I believe that concrete-paved trails should also be aligned with the informal porous edge as well.  The breeze/ decomposed granite provides a surface that has less impact on runners knees and joints, most runners will choose to run on this surface when given a choice.  This allows the remainder of the trail area to be used for walking, bicycles and strollers.