Between 2011 and 2014, the morning commute on the Katy Freeway in Houston lengthened by 25 minutes across two segments monitored by local authorities, a 30% increase. The road in question is no merely poorly maintained rural highway: it is Interstate 10, widened to 26 lanes when counting the ramps, at a cost of nearly $3 billion. The project, undertaken from 2003 to 2008, carried a single stated objective: to end the traffic jams.
26 lanes, and yet the clock kept climbing.
- The Houston I-10 was widened to 26 lanes, counting the ramps, at a cost of nearly $3 billion.
- Between 2011 and 2014, the morning commute on two segments rose by 25 minutes, a 30% increase.
- Induced demand explains much of this phenomenon: more space attracts more vehicles.
A Bottleneck Designed for 80,000 Vehicles per Day
To understand the Texan bet, one must start from the original arithmetic. Designed in the 1960s for around 80,000 vehicles per day, this highway links downtown Houston to Katy, in the western suburbs.
In the 2000s, it carried about 250,000.
Facing traffic more than three times the anticipated volume, the State of Texas opened its wallet: construction from 2003 to 2008, up to 26 lanes, nearly $3 billion. The reasoning rested on a plumbing image: replacing a too-narrow pipe with a wider one. At the opening, enthusiasm ran high, and early travel times gave the impression that the engineers had been right. The trend, however, reversed a few years later.
A note on the 26-lane figure: it counts ramps and applies only to certain segments, as Bloomberg CityLab notes. Other tallies, such as Strong Towns’, mention 23 lanes and $2.3 billion, while the most cited sources, including Slate, stay with 26 lanes and nearly $3 billion.
46 Minutes in 2011, 70 Minutes in 2014
The local group Houston Tomorrow compared travel times for a downtown-to-downtown route: 46 minutes in 2011, 70 minutes in 2014. That’s 24 minutes more in three years on an already-widened freeway. These comparisons rely on Transtar data, Houston’s official traffic-tracking system.
Analyst Joe Cortright of City Observatory used these same data in 2015 for two segments of the Katy Freeway. In the morning, the trip gains 25 minutes, or 30%. In the evening, it gains 23, or 55%. These figures were later picked up by Strong Towns, then cited by Slate.
Morning and evening, this adds up to 48 minutes more per day.
For a driver making this trip every weekday, that amounts to 4 extra hours behind the wheel per week, nearly 200 hours in a 48-week year, equivalent to more than 8 whole days. A methodological note is warranted: the comparison covers 2011-2014 and not the situation before the project, since it begins three years after the completion of the works. Bloomberg CityLab, in 2016, noted peak times rising between those two years.
Other factors may have contributed, led by the growth of the western suburban population, and no figure in this series allows disentangling each contribution. What remains is that the relief of the early years faded on these two segments.
The Induced Demand, Plain Language
When you add capacity to a road, there are always more cars to occupy it: this is the principle of induced demand. Drivers who had avoided the corridor during busy hours return, others set out because the trip now seems reasonable. And along the corridor, developers build housing and shops, which in turn bring more vehicles.
Think of a belt that’s loosened a notch after a big meal. The relief is real, but it prompts you to go back for more. An expanded highway works the same way, since the extra space invites more driving and living farther away. Around Interstate 10, developers gradually added more shops and housing.
In 2011, economists Gilles Duranton and Matthew Turner named this mechanism: the fundamental law of road congestion. Their study, focusing on American city highways, concluded that traffic increases roughly in the same proportion as the miles of roads. Adding 10% more lanes tends to yield about 10% more vehicles on the road.
Reading an Expansion Project with Another Perspective
The next time an expansion is announced near you, two questions are worth asking: what new traffic will the project attract, and what will be built along the road? A promised time savings should be judged over several years, not just the first months after opening, and the dossier should specify the reference year and the time of day measured. The 46 minutes in 2011 only make sense in light of the 70 minutes in 2014. The same caution applies to the 26 lanes, which count the ramps, and to the 30% figure, which applies to two segments between 2011 and 2014.
In February 2016, Houston’s new mayor, Sylvester Turner, urged the Texas Department of Transportation to stop focusing on highway widening, according to Bloomberg. A month later, on March 4, 2016, he cited the Katy Freeway, up to 26 lanes counting the service roads, to remind that the expansion completed in 2008 left drivers in peak-hour traffic and urged other congestion-fighting approaches.
Sources: blogs.cornell.edu | kinder.rice.edu | quebecnouvelles.com
