**The Best of Creative Computing Volume 1 (published 1976)**

EXERCISE 11 – Closing Down Freeways Use the program from Exercise 8 and any wind velocity you desire. What happens to C if the freeways are shut down at some particular instant? Sketch a rough graph of the program printout. We still have serious flaws in our automobile air pollution model. We have been assuming constant values of N, W, and R2. Clearly, this isn't realistic. It is common experience that there are morning and afternoon traffic rush hours, and that very little traffic is on the street in the middle of the night. Also, the wind rarely blows with constant velocity. Finally, the dissipation rate R2 is certainly not constant. As we discussed previously, photochemical smog is the result of organics, oxides or nitrogen and sunlight. It stands to reason that R2 should be smaller during hours of sunlight than during hours of darkness. It will be fairly easy to take these ideas into account and make our model much more realistic. The key is to assume maximum values of N, W, and R2, then take hourly decimal parts of the maximum values. Thus we can set up one list of 24 factors to be applied to N, another list for W, and so on. Each of these lists constitutes a time profile of each factor. Now, the model is Pnew = Pold + XiN – YiWPold/50 – ZiR2Pold. (4) Xi is the traffic profile factor (applied to N), Yi is the wind profile factor, and Zi is the dissipation profile factor. The subscript i is the hour number (1 to 24). So we can compare results, let's agree that hour number 1 in any day is from midnight to 1 a.m. EXERCISE 12 – A Time Dependent Model Write a BASIC program to evaluate the model given by (4) applied to the freeway example in Exercise 8. Assume reasonable sets of values for X, Y, and Z. Print out C every hour. Sketch your result in a simple graph. EXERCISE 13 – Political Questions Use the model developed in Exercise 12 on a system whose characteristics are specified by you. Run the program to get a feel for the pollutant concentrations that come out of the model. Now, suppose that the edict has come down to cut down on pollution. Use your model and program to investigate the question. Make realistic suggestions as to how the pollution concentration from automobiles might be cut down. [image] INFLATION POLLUTION DRUG ABUSE KEEP AMERICA BEAUTIFUL