I-45 in Houston: traffic, congestion, safety and the NHHIP rebuild

Interstate 45 is Houston’s north-south interstate. Its busiest Harris County count station averaged 271,938 vehicles a day in 2025.¹ Construction on the Texas Department of Transportation’s (TxDOT) North Houston Highway Improvement Project (NHHIP) began in October 2024.²

North Freeway and Gulf Freeway: I-45’s Houston segments

North of downtown, I-45 is the North Freeway. It meets I-10 near downtown, crosses the 610 North Loop and Beltway 8 North, and continues into Montgomery County toward Conroe. Southeast of downtown it is the Gulf Freeway, which crosses the 610 South Loop and Beltway 8 Southeast on its way to Galveston.³

Around downtown, I-45 runs on the Pierce Elevated along the west and south sides of the central business district. The NHHIP would move I-45 next to I-10 and I-69 and end the Pierce Elevated’s use as a highway.²

I-45 traffic counts

The three busiest stations on I-45 in Harris County are all on the North Freeway, near Resthaven Cemetery and exits 63 and 64. From 2024 to 2025 the top station rose 2.2% and the busiest Gulf Freeway station slipped 0.7%, by Texas Mobility Outlook’s arithmetic from TxDOT’s annual average daily traffic (AADT) counts.¹

I-45 truck traffic

TxDOT’s 24-hour classification count on the North Freeway near Resthaven Cemetery found 21,275 trucks among 263,458 vehicles on April 30, 2025, or 8.08%. Tractor-trailers and other combination trucks made up 61.7% of those trucks. On the Gulf Freeway near Santa Elena St the same day, trucks were 5.59% of traffic and combination trucks 40.3% of trucks.⁴ The shares of trucks are computed by Texas Mobility Outlook.

In Montgomery County, counts found higher truck shares: 11.05% (March 2024) and 13.73% (May 2025).

I-45 congestion rankings

The Gulf Freeway from I-10 to the 610 South Loop is I-45’s most congested section in the 2025 ranking by the Texas A&M Transportation Institute (TTI), which uses 2024 traffic. It moved into the statewide top 10 at No. 7, up from No. 14.⁵ Its $198.3 million congestion cost is the highest of any Houston-area segment on the list, by Texas Mobility Outlook’s reading of TTI’s table.³

For trucks, TTI ranks the same Gulf Freeway section 23rd in Texas, the North Freeway from Beltway 8 to I-610 27th and the North Freeway from I-610 to I-10 41st.³

What the NHHIP will build

TxDOT divides the project into three segments: Beltway 8 North to I-610 (Segment 1), I-610 to I-10 (Segment 2), and a downtown loop system covering I-45, I-10 and US 59/I-69 (Segment 3).⁶ Its main elements:

• Four non-tolled managed lanes, two in each direction, open around the clock to carpools and transit, from Beltway 8 North to downtown and along US 59/I-69 to Spur 527.
• I-45 rerouted to run parallel to I-10 on the north side of downtown and to US 59/I-69 on the east side.
• Four I-10 express lanes between I-45 and US 59/I-69, and a rebuilt I-45 interchange at the 610 North Loop.⁶
• On I-69 downtown, “lanes will increase from 8 to 10 or 12 in each direction,” in TxDOT’s words.²

TxDOT says the Pierce Elevated “will no longer serve a transportation function and could be removed or repurposed.”²

NHHIP cost: $9.47 billion, and why TxDOT figures differ

TxDOT’s August 2026 construction phasing graphic lists an estimated contract cost for each of the 14 projects. They add up to $9,474,699,000, Texas Mobility Outlook’s sum.⁷ Other TxDOT pages give different numbers:

• Segment 1: “$1.15 billion” in the segment page’s text, but “Total cost = $907,200,000” on the same page. The graphic’s three projects sum to $1.147 billion.⁸
• Segment 2: $1.62 billion on the segment page; $1,698,200,000 on TxDOT’s Texas Clear Lanes page, which matches the graphic.^9,10
• Project 3A (I-69, SH 288 to Spur 527): $850.5 million on the graphic, $771.8 million on Texas Clear Lanes, and $742.1 million in a TxDOT Connect project record updated Oct. 2, 2026.^7,10,11
• Project 3B-2 (I-69, SH 288 to I-45): $695.5 million on the graphic and Texas Clear Lanes; a TxDOT Connect record last updated in September 2024 lists $549.0 million.¹¹

Texas Mobility Outlook uses the graphic because it is the only TxDOT source that prices all 14 projects at one date.

NHHIP construction schedule

Sources: TxDOT project timeline, segment and project pages, and TxDOT Connect.^2,7,8,9,11 The graphic’s bar ends are read visually and are approximate. Texas Clear Lanes gives 3B-2 a 2032-2035 timeline, which conflicts with the January 2025 start on the NHHIP site.¹⁰

At an April 28, 2026 public meeting, TxDOT proposed changes to 3C-1 on I-10 between Gregg St and Waco St: an outfall channel to Buffalo Bayou and a pump station, needing 1.18 more acres of right of way, with one potential residential displacement.¹²

I-45 safety data and the “deadliest highway” claim

TxDOT’s published crash tables do not break out I-45. The nearest official figure is the road-class count: 134 people died on Harris County’s interstates in 2025, a total that combines I-45 with every other Interstate highway in the county.¹³

Results that name I-45 come from third-party analyses of National Highway Traffic Safety Administration (NHTSA) data:

• A law firm’s marketing study ranked I-45 from exit 49B to exit 60A as the deadliest 10-mile highway segment in the U.S., with 142 fatal crashes in 2000-2019.¹⁴
• A study commissioned by a bail bond company counted 88 fatal crashes on I-45 in Houston in 2019-2023, first in Texas, as reported by CultureMap Houston.¹⁵
• A personal-finance company placed two five-mile I-45 stretches among Texas’ 10 deadliest for 2017-2019, as reported by FOX 26 Houston.¹⁶

The claim that I-45 is America’s deadliest highway began with a 2016 ValuePenguin ranking of 2011-2015 data, in which I-45 was second, measured by fatal crashes per 100 miles of road.¹⁷ Later articles moved it to first and dropped the years. The research note Is I-45 the deadliest highway in America? traces the statistic, and Houston’s most dangerous highways compares every published ranking.

Work zones on I-45

TxDOT counts work zone crashes by county, not by road. Harris County had 1,525 work zone crashes in 2025 and 14 work zone deaths, up from 10 deaths in 2024.^18,19 NHHIP work under way in fall 2026 includes a Chartres St closure from Aug. 3, 2026 to Jan. 31, 2027 and the rebuild of the Alabama St bridge through Feb. 8, 2027.²⁰ Houston highway construction and work zone crashes covers the county figures.

Hazmat rules on I-45

A City of Houston ordinance dated March 4, 1970 prohibits non-radioactive hazardous materials on I-45 from Franklin St to US 59, and the 610 Loop is the city’s designated through route.²¹ The Houston Police Department describes the Pierce Elevated as a restricted hazmat route.²²

Outside Houston, TxDOT’s route records list I-45 as a designated through route in Conroe, League City and La Marque. In Galveston, parts of I-45 are a through route, but hazmat is prohibited on I-45 from SH 342 to the west city limits during a 30-hour hurricane warning.²¹ The NHHIP’s cost by project is tracked with other corridors on Houston highway projects.