Traffic in the Lincoln Tunnel: Characteristics of traffic flow include density D, which is the number of cars per mile, and average speed s in miles per hour. Traffic system engineers have...

Traffic in the Lincoln Tunnel: Characteristics of traffic flow include density D, which is the number of cars per mile, and average speed s in miles per hour. Traffic system engineers have investigated several methods for relating density to average speed. One study23 considered traffic flow in the north tube of the Lincoln Tunnel and fitted an exponential function to observed data. Those data are partially presented in the table on the following page.

a. Make an approximate exponential model of D as a function of s.

b. Express using functional notation the density of traffic flow when the average speed is 28 miles per hour, and then calculate that density.

c. If average speed increases by 1 mile per hour, what can be said about density?