Z:gnu-www-ja-dat--c8c7e9-For example, you can make traf/en

For example, you can make traffic flow more smoothly by improving roads. Adding one lane to 20 miles of congested roads in a city might increase the average traffic speed by 15 miles an hour. Adding a second lane to those roads will not give the same improvement; this might increase the average speed by only 5 more miles an hour. The next additional lane might make no noticeable difference if the traffic jams are already gone. Yet each successive lane will cause greater dislocation as more and more buildings must be torn down to make room.