The Speed Trap Nobody Saw Coming
Travelers on Interstate 70 through central Indiana during the 1970s and 1980s often complained about a peculiar stretch of highway just west of Indianapolis. For no apparent reason, the speed limit would suddenly drop from 70 mph to 45 mph for exactly 1.3 miles, then jump back up again.
State highway officials insisted they had nothing to do with the speed reduction. Federal transportation authorities claimed it wasn't their jurisdiction. Meanwhile, the tiny town of Plainfield — population 387 — quietly collected nearly $2 million in speeding fines from confused motorists who had no idea they were driving through a municipal speed zone on a federal interstate.
It took twenty years for anyone in Washington to figure out what was happening.
When Surveying Goes Wrong
The confusion began in 1962, when the Interstate Highway System reached central Indiana. Interstate 70 was designed to bypass small communities entirely, running through rural farmland and avoiding the complications of municipal boundaries.
But when surveyors mapped the route west of Indianapolis, they encountered an unusual problem. The proposed highway corridor crossed a disputed boundary between Hendricks County and Marion County — a boundary that had been contested since the 1920s over a series of property tax disagreements.
Rather than delay construction while lawyers sorted out the county line, the Federal Highway Administration instructed surveyors to use the "most recent available municipal boundary maps." Unfortunately, those maps were from 1959, and they showed the town of Plainfield's limits extending much further north than anyone realized.
The highway was built according to those outdated maps, placing 1.3 miles of Interstate 70 technically within Plainfield's municipal boundaries.
The Discovery
Plainfield's town clerk, Martha Henderson, discovered the highway situation entirely by accident in 1966. She was updating municipal tax records when she noticed that several parcels of land on both sides of the new interstate were listed as being within town limits.
Curious, she drove out to investigate and found herself looking at a busy federal highway that, according to her maps, belonged to her tiny farming community.
Henderson brought the discovery to the town council, where it sparked the kind of heated debate that only small-town politics can produce. Some members argued they should notify state and federal authorities immediately. Others suggested they should explore what municipal authority over a federal highway might actually mean.
The "explore first" faction won.
Testing the Waters
Plainfield's first experiment was modest: they posted a single 55 mph speed limit sign on their section of I-70, reducing it from the federal standard of 70 mph. Then they waited to see what would happen.
Nothing happened. No federal agents arrived to remove the sign. No state troopers objected. Motorists simply slowed down and continued on their way.
Emboldened, the town council authorized Police Chief Robert Kramer to begin writing speeding tickets on "their" section of highway. The first citation was issued on September 12, 1967, to a truck driver from Ohio who was traveling 72 mph in what was now a 55 mph zone.
The driver paid the $35 fine without question.
Twenty Years of Highway Authority
What followed was perhaps the most profitable municipal traffic enforcement program in American history.
Plainfield gradually reduced their highway speed limit to 45 mph, creating a dramatic speed differential that caught thousands of drivers off guard. They installed their own traffic signs, painted municipal parking spaces at highway rest areas, and even established their own towing contracts for disabled vehicles.
The town's three-person police force spent most of their time on highway patrol duty. Chief Kramer purchased two additional patrol cars and hired four part-time officers specifically to handle interstate traffic enforcement.
By the mid-1980s, highway citations accounted for 78% of Plainfield's municipal revenue. The town used the money to build a new city hall, upgrade their water system, and establish a volunteer fire department.
The Paper Trail
The most remarkable aspect of Plainfield's highway operation was how thoroughly they documented everything. Town meeting minutes from this period read like a masterclass in creative municipal law.
In 1974, the council formally designated their section of I-70 as "Plainfield Municipal Highway Extension 1," complete with its own maintenance budget and snow removal contracts. They negotiated with the state to handle major repairs while maintaining authority over traffic enforcement and signage.
When the Federal Highway Administration conducted routine inspections, Plainfield officials simply presented themselves as "local municipal contractors" handling traffic management services. Since small towns often contracted with state and federal agencies for various services, nobody questioned the arrangement.
The town even established its own highway court, with Mayor Dorothy Mills serving as traffic judge every Tuesday evening in the basement of the Methodist church.
The Reckoning
Plainfield's highway empire finally ended in 1987, when a frustrated motorist decided to fight his speeding ticket all the way to federal court.
Truck driver James Morrison had been cited for traveling 68 mph in Plainfield's 45 mph zone. But Morrison was a former military police officer who knew something about traffic law, and he couldn't understand how a municipal court had jurisdiction over a federal interstate highway.
Morrison's lawyer requested all documentation proving Plainfield's authority over I-70. That's when federal transportation officials discovered, to their considerable embarrassment, that they had been allowing a tiny Indiana town to regulate interstate commerce for two decades.
Fixing the Unfixable
Resolving Plainfield's highway situation required an act of Congress — literally.
The Federal Highway Administration couldn't simply reclaim the highway, because Plainfield had legitimate legal authority based on the original surveying error. The town couldn't voluntarily surrender jurisdiction, because they had outstanding municipal bonds backed by highway citation revenue.
Congress eventually passed special legislation in 1988 that compensated Plainfield $750,000 for surrendering their highway authority while protecting the validity of citations already issued. The town was allowed to keep all fines collected before the federal takeover.
The Aftermath
Today, that stretch of Interstate 70 maintains a consistent 70 mph speed limit, and travelers pass through without realizing they're driving over one of the strangest chapters in American transportation history.
Plainfield used their federal settlement money to establish a municipal development fund that still supports local projects. The town's population has grown to nearly 30,000, though longtime residents still refer to the 1970s and 1980s as "the highway years."
Former Police Chief Kramer, now retired, keeps a framed copy of the last speeding ticket issued under Plainfield's authority in his living room. "People always ask me if we knew we were doing something wrong," he said in a 2010 interview. "But we weren't doing anything wrong. We were just doing our job — it was everyone else's job that was wrong."
The Lesson in the Asphalt
The Plainfield highway case became a cautionary tale taught in public administration programs across the country. It demonstrates how bureaucratic gaps can create opportunities for creative interpretation of authority — and how those interpretations can persist for decades when nobody's paying attention.
More importantly, it raises questions about the nature of jurisdiction itself. If a small town can successfully regulate a federal highway for twenty years, collect millions in fines, and provide effective traffic enforcement services, what does that say about our assumptions regarding which level of government should handle which responsibilities?
Plainfield proved that sometimes the most unlikely authorities can be surprisingly effective — even when nobody intended to give them authority in the first place.
