UNITED STATES—

Key Findings

91.6% of California’s high-traffic bridges (those carrying 100,000+ vehicles daily) have exceeded their 50-year design life.

5 bridges are at least 100 years old and still carry a combined 648,000 vehicles daily.

California accounts for 27.2% of all high-traffic bridges nationwide and 34.4% of all high-traffic bridge crossings.

78.6% of the state’s high-traffic bridges were built during a single 20-year window (1950–1969), and every one of them is now over 55 years old.

The oldest high-traffic bridge in California, Irwin Creek, was built in 1895 and still carries 129,000 vehicles daily.

California’s drivers cross aging bridge infrastructure at a scale unmatched anywhere in the country. A state-level analysis of federal bridge data reveals that more than nine out of every ten high-traffic bridges in California, structures carrying over 100,000 vehicles daily, were built more than 50 years ago, with the oldest dating back to the 19th century while still handling modern freeway-level traffic volumes.

The study, conducted by Beck & Beck, analyzed National Bridge Inventory (NBI) data from the Federal Highway Administration, filtering for California bridges with Average Daily Traffic (ADT) exceeding 100,000 vehicles and calculating bridge age based on year built.

California vs. the Nation: A Disproportionate Burden

California is home to 1,395 high-traffic bridges, 2.4 times more than second-place Texas (589) and more than the next three states combined. These structures carry 262.6 million vehicle crossings every day, representing 34.4% of all high-traffic bridge crossings nationwide despite California being one of 45 states and territories with such bridges. The state’s average bridge age of 63.0 years also exceeds the national average of 56.3 years.

Top 10 Oldest High-Traffic Bridges in California

Rank Bridge Name Year Built Age Daily Traffic
1 Irwin Creek 1895 131 yrs 129,000
2 Strawberry Creek 1924 102 yrs 131,000
3 Branciforte Creek 1924 102 yrs 100,000
4 Beanfield Drain 1926 100 yrs 144,000
5 Tamarisk Drain 1926 100 yrs 144,000
6 Agua Chinon Wash 1927 99 yrs 201,000
7 Alameda Creek 1927 99 yrs 141,000
8 San Mateo Creek 1928 98 yrs 236,000
9 Transmission Canal 1928 98 yrs 232,000
10 Green Valley Creek 1928 98 yrs 189,000

The Irwin Creek bridge, built in 1895, predates widespread automobile use by over a decade and still carries 129,000 vehicles daily. Five California bridges have reached or exceeded the century mark, and all ten of the state’s oldest high-traffic bridges were built before 1930, meaning every one of them is at least 96 years old.

Top 10 Busiest High-Traffic Bridges in California

Rank Bridge Name Year Built Age Daily Traffic
1 Gilman Street 1955 71 yrs 550,000
2 Powell Street 1954 72 yrs 531,000
3 Buried Walkway 1954 72 yrs 531,000
4 Bolsa Chica Ditch 1959 67 yrs 374,000
5 Route 55 1955 71 yrs 329,500
6 La Paz Rd 1959 67 yrs 327,000
7 Patt Drain #4 1959 67 yrs 319,000
8 Patt Drain #5 1959 67 yrs 319,000
9 Patt Drain #6 1959 67 yrs 319,000
10 Washington Blvd 1954 72 yrs 300,000

The Gilman Street bridge, built in 1955, carries a staggering 550,000 vehicles daily, the highest volume of any bridge in the state, at 71 years old. Every one of the ten busiest bridges in California was built between 1954 and 1959. None is younger than 67 years old.

“When California’s busiest bridge was built during the Eisenhower administration and is still carrying over half a million vehicles a day, it tells you how far behind the state’s infrastructure investment has fallen. These bridges were engineered for mid-century traffic patterns, not for the volumes and vehicle weights they’re handling today. Drivers involved in accidents on aging infrastructure may face unique challenges in determining liability.”

— John Beck, Attorney & Founding Partner, Beck & Beck

 

California High-Traffic Bridge Age Distribution

Age Category Bridge Count % of Total Combined Daily Traffic
100+ years 5 0.4% 648,000
70–99 years 298 21.4% 57,375,714
50–69 years 986 70.7% 192,255,951
30–49 years 71 5.1% 8,226,550
Under 30 years 35 2.5% 4,108,670

The overwhelming majority of California’s high-traffic bridges, 91.6%, are over 50 years old, far exceeding the 76.1% national rate. Just 2.5% of the state’s high-traffic bridges were built within the last 30 years.

When California’s Bridges Were Built: Construction Era Breakdown

Construction Era Bridge Count % of Total Combined Daily Traffic
Pre-1930 12 0.9% 1,958,000
1930–1949 77 5.5% 13,987,352
1950–1959 403 28.9% 82,717,347
1960–1969 694 49.7% 139,411,903
1970–1979 119 8.5% 14,089,063
1980–1999 61 4.4% 7,030,050
2000–Present 29 2.1% 3,421,170

A striking 78.6% of California’s high-traffic bridges were built in just two decades: the 1950s and 1960s, coinciding with the state’s postwar population boom and the construction of the Interstate Highway System. These 1,097 bridges now carry 222.1 million vehicles daily, and every single one has exceeded its original 50-year design life.

Top 10 Pre-1950 Bridges Still Carrying 100,000+ Vehicles Daily

Rank Bridge Name Year Built Age Daily Traffic
1 Irwin Creek 1895 131 yrs 129,000
2 Strawberry Creek 1924 102 yrs 131,000
3 Branciforte Creek 1924 102 yrs 100,000
4 Beanfield Drain 1926 100 yrs 144,000
5 Tamarisk Drain 1926 100 yrs 144,000
6 Agua Chinon Wash 1927 99 yrs 201,000
7 Alameda Creek 1927 99 yrs 141,000
8 San Mateo Creek 1928 98 yrs 236,000
9 Transmission Canal 1928 98 yrs 232,000
10 Green Valley Creek 1928 98 yrs 189,000

California has 89 pre-1950 bridges still carrying over 100,000 vehicles daily, with a combined daily traffic load of nearly 15.9 million crossings. The Temescal Creek bridge, built in 1936, handles the heaviest load among pre-1950 structures at 288,000 vehicles per day.

California High-Traffic Bridge Data at a Glance

Metric Value
Total High-Traffic Bridges (ADT ≥ 100K) 1,395
Total Daily Vehicle Crossings 262,614,885
Share of National High-Traffic Bridges 27.2%
Share of National High-Traffic Crossings 34.4%
Average Bridge Age 63.0 years
Median Bridge Age 64 years
Bridges Over 50 Years Old 1,278 (91.6%)
Bridges Over 70 Years Old 238 (17.1%)
Century-Old Bridges (100+ years) 5
Pre-1960 Bridges 492 (35.3%)
Pre-1960 Daily Traffic 98,662,699
Oldest Bridge Year 1895
Newest Bridge Year 2022

Methodology

Study Overview

Beck & Beck analyzed official bridge inventory data from the Federal Highway Administration’s National Bridge Inventory (NBI) 2025 data release to identify high-traffic bridges across the United States and assess their age characteristics.

Data Collection Process

Primary Data Source: Federal Highway Administration National Bridge Inventory (NBI) ASCII Data 2025. Geographic Scope: All 50 U.S. states plus District of Columbia and Puerto Rico. Reference Year: 2026 (for age calculations).

Filtering Methodology

Average Daily Traffic (ADT): Only bridges with ADT => 100,000 vehicles were included to focus on high-traffic structures. Year Built: Used to establish bridge age and identify oldest structures still in service. Bridge Age Calculation: Current Bridge Age = 2026 – Year Built.

Calculation Methodology

State Rankings: Determined by total count of high-traffic bridges meeting ADT threshold. Average Bridge Age: Calculated as mean of all bridge ages within each state. Pre-1960 Bridges: Count of bridges with Year Built < 1960 for each state.

Data Sources

Primary Source: Federal Highway Administration National Bridge Inventory (NBI): https://www.fhwa.dot.gov/bridge/nbi/ascii2025.cfm

Research Dataset: https://docs.google.com/spreadsheets/d/1J7QzOjCxivpCzNycVuxhwcgsJ_1tMtZl/edit?gid=2095776817#gid=2095776817

Study by: https://becklawmo.com/

About Beck & Beck

Beck & Beck, Missouri Car Accident Lawyers, is an experienced law firm focused on vehicle accident representation. The firm supports clients from early claim evaluation through medical care coordination and insurance negotiations, advocating aggressively for fair outcomes after serious crashes. For more information or media inquiries related to this report, contact our team. For more information, visit https://becklawmo.com/