Intersection Gridlock Analysis at Donohoe St and Highway 101 NB Off-Ramp

Christopher Kao -

Executive Summary

Drone footage and observational analysis reveal that vehicles are regularly blocking the intersection at Donohoe Street and the Highway 101 northbound off-ramp during peak commute hours. This behavior causes significant delays for East Palo Alto residents and reduces the overall efficiency of the intersection. This report proposes low-cost enforcement and design interventions to improve traffic flow and reduce commuter delays.

Context

I have personally observed the bottleneck of traffic while driving on Donohoe St in front of the Amazon building at 2100 University Ave during morning and evening rush hour commutes. A number of East Palo Alto residents had requested that I analyze the intersection by drone.

While it wasn’t clear to me when I was driving on Donohoe EB before why it took me 10 minutes to cross this intersection, after recording the drone video I see why: it’s because of cars consistently blocking the keep clear. Some drivers enter the intersection despite the “Keep Clear” markings, gaining a small personal time advantage while collectively increasing delays for many other drivers. This imbalance results in significant cumulative time loss for the community.

Observed Problem

Vehicles at Donohoe & Highway 101 NB Off Ramp are consistently blocking the intersection box which is marked with Keep Clear (Fig 2). As a result, the intersection is not moving as many vehicles as it should be, which is adding a few minutes to every person’s commute. 

The problem is worse during evening rush hour. This aligns with the fact that 20% more cars use Cooley Ave in the evening peak hour than in the morning peak hour (Table 2 of 2020 Mobility Study), probably because the Dumbarton Bridge tolls only in the morning direction from East Bay to Peninsula.

  • During the morning rush hour, vehicles going on Donohoe WB are blocked.
  • During the evening rush hour, vehicles going on both Donohoe WB and EB are blocked. 

Detailed Observations

Morning Rush Hour

I took this drone video on Tuesday, May 20, 2025 at 8:51am.

Fig 1. During the morning rush hour, vehicles that came from the right (in green) block the intersection box (5:19 in video). 

Timestamp Donohoe WB Blocked Donohoe EB Blocked Description
1:29 ✅ 2 yellow cars blocked a red car from making a right onto Donohoe WB.
3:17 ✅ 3 cars blocked the intersection, causing a 15-second delay for yellow cars turning left onto Donohoe WB.
5:19 ✅ 2 cars blocked the intersection, delaying yellow cars turning left by ~8 seconds. Without the blockage, they could have moved at normal speed.
6:09 ✅ 5 cars blocked the intersection, causing a 24-second delay for the red van turning right onto Donohoe WB.
7:59 ✅ 2 cars blocked the intersection, causing a 15-second delay for left-turning cars.

Evening Rush Hour

I took this drone video on Monday, May 19, 2025 at 4:02pm.

Fig 2. During the evening rush hour (1:16 into video), vehicles highlighted in yellow which had blocked the intersection box are impeding the vehicles highlighted in blue (Donohoe EB). 

Timestamp Donohoe WB Blocked Donohoe EB Blocked Description
1:08 ✅ 3 drivers from Highway 101 NB off-ramp entered the intersection to join the EB left-turn queue onto Cooley Ave NB, entirely blocking Donohoe EB.
2:41, 2:52 ✅ 7 drivers on Donohoe WB blocked the box, preventing both NB off-ramp left-turn lanes from moving for ~30s. Right turn lane on WB was empty and underused.
5:13 ✅ 7 drivers on Donohoe WB blocked the box, delaying yellow-annotated cars by 15s.
7:36 ✅ 6 drivers on Donohoe WB blocked the box, delaying yellow-annotated cars by 8s.
8:27 ✅ 2 yellow cars blocked the intersection, obstructing Donohoe EB traffic.

Impacts

Based on an estimated 2,103 drivers per peak hour period (Table 2 of 2020 Mobility Study) for 4 peak hours, with ⅓ of the vehicles experiencing a 2-minute delay over 250 work days/year, at a load factor of 1.2 passengers per vehicle, this results in 416,394 hours of lost time. At $20/hour, this equates to $8,327,880 annually in lost productivity.

Moreover, this inefficiency mainly impacts drivers making trips to/from EPA (84%) - as opposed to cut through drivers (16%) - because the 2020 Mobility Study (Table 2 of 2020 Mobility Study) showed that 340 out of the 2,103 PM peak hour trips on Donohoe St west of Cooley Ave is cut through.

This results in $8,327,880 * 84% = $7M annually in lost productivity to people making trips to/from East Palo Alto. 

Recommendations

  1. Enforcement
    1. Short-term: Partner with East Palo Alto Police Department for periodic presence during peak hours. As an idea, the police vehicle could be stationed in the Amazon driveway, for clear visibility and clear access into the intersection.
    2. Long-term: Consider installing automated camera enforcement (if legal).
  2. Physical design changes
    1. Repaint “KEEP CLEAR” zone with high-visibility markings.
    2. Add signage alerting drivers to the enforcement zone.
    3. Consider road markings to delineate intersection box boundaries.
  3. Data-driven evaluation
    1. Use drone footage pre/post intervention to quantify improvement.
    2. Publish results to foster public support and accountability.

Call to Action

Do you have any thoughts or suggestions? Please comment below.