A city is planning to install new traffic lights at 100 intersections to improve safety and reduce congestion. Each traffic light system costs $25,000 to purchase and install, and has an expected lifespan of 15 years. The city also needs to hire additional staff to maintain and repair the traffic lights, with each technician earning an annual salary of $40,000. Estimate the total cost of implementing and maintaining this new traffic light system over its 15-year lifespan.

First, let's find the total cost of purchasing and installing the traffic lights at all 100 intersections: 100 * $25,000 = $2,500,000.

Next, we need to determine how many technicians are needed. Since each technician can maintain 20 traffic lights, we'll divide the number of traffic lights by the number of traffic lights per technician: 100 / 20 = 5 technicians.

Now, let's calculate the annual salary for all 5 technicians combined: 5 * $40,000 = $200,000.

Over a 15-year lifespan, the technicians will earn a total of 15 * $200,000 = $3,000,000 in salaries.

Finally, add the initial installation cost and the total salary cost over 15 years to find the total cost of implementing and maintaining the new traffic light system: $2,500,000 + $3,000,000 = $5,500,000.