Slow-moving amphibians are particularly vulnerable to road-related mortality. Our team has documented massive Pacific Newt roadkill on Alma Bridge Rd. at Lexington Reservoir, CA since 2017.
In order to devise effective mitigation strategies to help the newts cross the road safely, it's important to understand traffic patterns in this area. We know that certain agencies have been collecting traffic data on Alma Bridge Rd., but we've been unable to obtain their data. So we started collecting our own data in 2019. However, our data are snapshots of mostly 2-hr windows of time during daylight hours two times per week. What we need is 24-hr surveillance 7 days/week over a period of months so that we can correlate newt roadkill with traffic patterns.
Who uses this road?
Residents, hikers, bikers, boaters, equestrians, Santa Clara County (SCC) Parks and Midpen rangers, PG&E, Vulcan Materials Co., San Jose Water Co., Los Gatos Rowing Club, UCSC Puma Project.
What We Know
Traffic is much heavier in the (recreational) northern half of Alma Bridge Rd. during daylight hours. Traffic is lighter in the (residential) southern half of the road.
** Our team documented a total of 1,469 motor vehicles during 55 surveys last year; 882 in the north; 587 in the south.
** 1,223 motor vehicles have been documented during 19 surveys this year; 922 in the north; 426 in the south.
Figure 1 shows the total traffic we've documented on Alma Bridge Rd. during our surveys. It shows heavier daytime traffic on the northern half of the road.
What We Suspect
Figure 2 begins to show what we've suspected - traffic has increased significantly over the years.
Confounding Issues
The Covid-19 Pandemic and associated business closures and lockdown orders have altered traffic patterns in the area since March 2020.
** @newtpatrol has noticed a significant increase in traffic in the southern half of our study area on weekdays during 2020 due to COVID-19.
Comments
Good job pulling these data together @truthseqr. I do hope that the data from the MidPen et al planned traffic count is released so we see a fuller 24/7 picture of road use.
Earlier in 2020 it seemed to me that COVID caused there to be way more traffic in the southern half on weekdays than I had been seeing previously. I don't know if that has continued.
One note is that Alma Bridge Road/Lexington is in Santa Clara county, not Santa Cruz. It is the case that many mountain people who do live across the border (which is approximately along Summit Road) in Santa Cruz county use Old Santa Cruz Highway to avoid highway 17 traffic during rush hour, but I don't think that most (or any) of them are going all the way around the back side of Lexington/Alma Bridge during that time.
@newtpatrol, thanks so much for sharing your observations. I'll add them to the list.
@newtpatrol, thanks for reminding me that I used the population stats for Santa Cruz County as a placeholder because I don't know how to get the population data for Lexington. The population info above came from Michael Hobbs' study of long-toed salamanders:
• Fall 2013 Amphibian Mortality on Roads: A Case Study in Santa Cruz Long-toed Salamander Habitat (Michael Thomas Hobbs, San Jose State University, 2013)
I'd really appreciate help in finding population trends for the Lexington area.
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