161 Traffic Collisions

Mount Diablo State Park from 2010 to 2017

On April 12, 2016, we submitted a Public Records Act Request to California State Parks for all collisions from 2014 to Present. 

  • It took 18 months, a letter from King & Spalding LLP and a possible lawsuit to finally obtain 49 Traffic Collision Reports (2014 to 10/23/17) We will publish the analysis of these 49 TCRs soon. 
  • In 2016, we were told by Park Leadership, "we made a mistake giving you the 112 Traffic Collision Reports for 2010 to 2014. We will not provide any more Traffic Collision Reports for Mount Diablo State Park." 

Public Records Act Request (April 2, 2015): One hundred and twelve MDSP Traffic Collision Reports (CHP 555) for North Gate Road, South Gate Road and Summit Road were completed and filed by MDSP Rangers. Traffic Collision Reports filed by CHP (the most serious collisions) and park ranger-investigated Trail Public Safety Reports involving Mountain Bike collisions occurring on unpaved roads were not included in this report.

112 collisions over a five years equals an average of approximately 1 collision every 2 weeks. According to Park Leadership, "if the number of non-reported paved-road collisions involving bicycles vs vehicles and solo bikes were included in this report, the overall totals would be significantly higher." 

MDSP Paved Road Collisions Report 2010 - 2014

  • Most cyclists had visible injuries (Minor/Moderate/Serious)
  • Most required medical responses: fire department, ambulance, and/or helicopter flights to local hospitals
  • CHP Commonality Factor: Most Collisions (82) occurred on or near Blind Curves
  • Bicycle vs. Vehicle (24) - Motorists at fault in 23 of these Collisions
  • Solo Bicycle (64) - Unsafe Speed (37); Other (27)
  • Vehicle vs. Vehicle (9)
  •  Solo Vehicle (10)   
  • Solo Motorcycle (5)       


Primary Collision Factors: Left of Center Line, Unsafe Passing, Passing without SufficientClearance, Unsafe Speed, Unsafe Turning, Tire Blowout, Mechanical, Distracted Driver, DUI, Bike vs. Deer, Vehicle backing up, Unknown

Day of Occurrence of Collisions: Saturday (43)  Sunday (34)  Monday (6)   Tuesday (7)   Wednesday (9)  Thursday (6) Friday (7) 

Most Likely Time of Day for  Collisions: Between 11 AM and 3 PM


Solo Bike Bicycle Collisions (2010 - 2014):

2010 (17)  

Prime Causes: Mechanical left pedal (1) , Adjusting glove (1), Unknown( 2), Tire blowout (4), Unsafe speed (9)

2011 (11)

Primary Causes: Looked back and hit a rock ( 1), Pedal Strap (1), Tire blowout (2), Unsafe speed (7)

2012 (13)

Primary Causes: Struck deer (1), Loose stem on handlebar(1), Rear wheel gave out (1), Tire blowout (2), Unsafe speed (6) Unknown (2)

2013 (11)

Primary Causes: Looked back at car (1), Loose gravel (1), Defective rear tire (1), Unsafe speed (7), Unknown (1)

2014 (13)

Primary Causes: Jacket wrapped around rear tire (1), Unknown (1), Defective front tire (1), Unsafe turning movement on dirt/gravel (1), Broken crank arm (1), Unsafe speed (8)

Most Likely Days(s) for Bicycle Paved Road Collision: Saturday and Sunday

Most Likely Time for Bicycle Paved Road Collision: Between 11am and 3pm

The document below, is the only analysis of Traffic Collisions on Mount Diablo from 2005 to the present conducted by Park Leadership from 2005 to April 2015.