Saturation Patrol Budget and Crash Data
Six months of crash data at the Route 1/Route 114 intersection show 54 crashes: 22 with injuries, 11 alcohol-involved, and 8 pedestrian-related. Of the 11 alcohol-involved crashes, 8 occurred Friday or Saturday between 2200 and 0200. The posted speed limit is 40 mph. You have four troopers and a $7,200 overtime budget. Each trooper earns $60 per hour in overtime. A saturation shift uses all four troopers for five hours. A speed display trailer costs $2,800 for a four-week deployment and requires no troopers. Department policy requires at least two troopers on any enforcement shift for officer safety. The intersection has no red-light camera. A business group has offered to pay for a second trailer, but not for overtime. Your captain wants a recommendation before the next weekend.
1. Calculate the cost of one saturation shift and the maximum number of full saturation shifts the budget allows. Show your work.
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One saturation shift costs 4 troopers x 5 hours x $60 per hour = $1,200. The budget is $7,200, so $7,200 / $1,200 = 6 full saturation shifts. If the department instead used only two troopers per shift, each shift would cost 2 x 5 x $60 = $600, allowing 12 shifts. But a saturation shift is defined as all four troopers, so the direct answer is 6 shifts. The two-trooper minimum is a safety floor, not a saturation plan. Also note that 6 shifts would use the entire budget and leave nothing for a trailer or for follow-up analysis.
2. Recommend an allocation of the $7,200 between saturation shifts and the trailer. Justify the trade-offs.
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Recommend 3 saturation shifts at $1,200 each, or $3,600, plus one trailer at $2,800, for $6,400 total and $800 remaining. The $800 cannot buy another full saturation shift, but it can cover one two-trooper shift at 2 x 5 x $60 = $600, leaving a small reserve. The trade-off is enforcement versus continuous visibility. Saturation shifts put troopers where alcohol-related crashes cluster Friday and Saturday 2200-0200; three shifts provide 60 trooper-hours of enforcement. The trailer is visible for four weeks and costs less than three full shifts, but it does not stop or cite drivers. Because 8 of 11 alcohol crashes are in the target window, I would place all three shifts in that window and use the trailer as a low-cost speed reminder. Accept the business group's second trailer rather than buying more overtime.
3. What percentage of crashes were alcohol-involved, and what additional data would most change your recommendation?
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Alcohol-involved crashes are 11 / 54 = 0.2037, or about 20.4 percent. Additional data that would change the recommendation: the number of injury crashes in the target window versus other times; whether the 8 alcohol crashes involved repeat locations or impaired drivers leaving specific businesses; traffic volume by hour so you can compute crash rate per 1,000 vehicles; and the trailer's measured speed reduction from prior deployments. If the 8 alcohol crashes are concentrated at one bar closing time, directed patrol may beat a trailer. If injury crashes are spread across the week, a trailer may be more cost-effective. The current data show association, not causation, so the recommendation should be framed as a test with a follow-up count.