The Appendix compares estimated yields and costs of 16 different congestion- and emission-charge strategies under assumptions described in Section I above. Their cost and yield estimates are drawn from three sources: (1) the Wilbur Smith Associates/Comsis studies performed for the REACH Task Force, applying congestion charges to freeways only; (2) the author's extrapolations of WSA estimates to include surface streets, as well as freeways; and (3) estimates by Elizabeth Deakin and Grieg Harvey for the California Air Resources Board (CARB) (CARB, 1995; see also Cameron, 1994, Harvey, 1994). For further details, request the longer version of this article.
Figure 1 (above) breaks out the estimated smog reduction yields of seven of the 16 strategies. A penny-per-average-mile emissions charge, variable by the emission level of each car, is about as high as the current "going rate" cost cutoffs for industrial polluters. By itself it would control more than $100 million worth of smog per workyear. So would a 15/30-cents a-mile peak-hour congestion charge on all roads, also by itself, assuming the charges had the same impact on surface streets as WSA calculated for freeways (See Appendix). A lower, freeways-only congestion charge would control just under $100 million worth of smog per workyear. Conclusion: either reasonable, "going-rate" emissions charges or reasonable congestion charges could cut smog damage by at least about $100 million a workyear. Deakin and Harvey say the control yield could be more than twice that figure for a 1-cent/mile emissions charge (Appendix), but let us leave that aside for the moment and suppose that $100 million is a conservative, round-number guess for the yield of either strategy by itself.
Figure 2 (below) is in some ways the most plainly revealing of pertinent tradeoffs. See Glossary, below, for full definitions of the various strategies. WSA means 'Wilbur Smith Associates." EM1 means "first emissions-charge variant." CP1 means "first congestion pricing variant," freeways only. WE means "Ward Elliott." CP3+ means "third WSA congestion-pricing variant, extended to surface streets." D-H Mod Combo means "Deakin-Harvey 'moderate-impact' combination." ET means $12.5 billion worth of "enhanced transit."
Figure 2: Gross Smog, Congestion Benefits, 2010, Selected Strategies
(1) none of the official WSA scenarios listed -- neither the reasonable, penny-a-mile emissions charge, which affects all roads, but is not time-specific, nor any of the congestion-charge combination scenarios, which are time-specific but affect freeways only -- has much effect on speed.
(2) the two scenarios combining reasonable penny-a-mile emissions charges with reasonable 10-30-cents-per-peak-mile systemwide congestion charges show enormous time savings, about 15 times greater in dollar value (at $6.80 per person hour per Section 1 above) than the very sizeable smog savings (at $9,000 to $21,000 per ton per Section 1) also produced. The lower estimate, WE CP3+, EM1, would save 680 million person hours a year, the higher, D-H mod, would save 950 million person hours a year (calculated from the Appendix). A third scenario, with 15-30-cents systemwide congestion charges, but no emissions charge at all, equals the WSA penny-a-mile emissions charge in smog reduction and produces 30 times as much savings from congestion relief. In each case, the higher figure (e.g., 30 cents a mile) is the charge for currently crowded links, the lower (10 cents a mile) is a "balancing" charge to keep traffic in charged crowded links from simply shifting to uncrowded links.