WisDOT Research Project 0092-25-23

Enhanced Light Crosswalk Illumination

Blue-spectrum lighting measurably improves nighttime pedestrian safety. Drivers detected pedestrians ~40 ft sooner than the existing baseline and ~26 ft sooner than 4000 K white, with faster reaction times.

281nighttime field rounds

2Wisconsin study sites

7spectral configurations

+19 ftearlier detection · Milwaukee

+63 ftearlier detection · Madison

Research Team

UW–Milwaukee · UW–Madison · TAPCO

Xiaowei (Tom) Shi, Ph.D.Principal InvestigatorAssistant Professor, UW–Milwaukee
tomshi@uwm.edu

Xiao Qin, P.E., Ph.D.Co-PIProfessor, UW–Milwaukee
qinx@uwm.edu

Xiaopeng Li, P.E., Ph.D.Co-PIProfessor, UW–Madison
xli2485@wisc.edu

Brian Scharles Sr.Co-PIDirector of Product Innovation, TAPCO
brians@tapconet.com

Muhammad FahadGraduate Research AssistantUW–Milwaukee
muhamm72@uwm.edu

Student team: Narayan Rai · Xiao Liang (UWM) · Bofeng Cao · Chengyuan Ma · Hangyu Li · Keke Long · Jiaxi Liu (UW–Madison) · Aleischa Kronshagen · Denise Lawien (TAPCO)
With sincere thanks to the WisDOT Project Oversight Committee and all participants.

Research problem

Improving pedestrian visibility at night

This project evaluates how enhanced crosswalk illumination influences driver detection and response at night. Using controlled field experiments, the team examines lighting spectrum, installation geometry, pedestrian characteristics, and roadside conditions.

The System

SafeWalk™ prototype with seven adjustable spectra

Purpose-built LED crosswalk illuminator (TAPCO SafeWalk 2.0), configured for field research.

SafeWalk crosswalk illuminators mounted on two poles lighting a pedestrian at a midblock crosswalk at night — SafeWalk™ crosswalk illuminator: dual-pole layout lighting the pedestrian, not just the pavement

≥ 20 lux vertical at pedestrian plane12–15 ft mountingAdjustable beam aiming25° × 24° beam · ≈820 cd/klmIP66 · −40°F to 176°F120 mph wind rating≈2 W per LED · 12 V DCSolar + battery compatible

Prototype spectral configurations assembled for testing — Prototype modules assembled for testing: 4000 K · 5000 K · 6500 K · RGB blue-light

Configuration	Type	Rationale
4000 K	Neutral white	FHWA / agency reference
5000 K	Cool white	One step above standard
6500 K	Daylight white	Upper white-light boundary
Blue Baseline	Blue-shifted LED	Reference blue configuration
Ice Blue	Blue-shifted LED	Blue + white mix, highest luminance
Sky Blue	Blue-shifted LED	Mid-intensity mix
Pure Royal Blue	Saturated blue	Maximum blue saturation

Seven spectral configurations: the agency-recommended white range plus the blue-shifted range never before field-tested in Wisconsin.

Field Testing

281 nighttime rounds at two Wisconsin sites

An instrumented probe vehicle approached the crosswalk while a mannequin on a remote-controlled electric skateboard crossed, creating repeatable pedestrian events on real roads, on real nights.

Madison site map and baseline lux measurement

Madison · 104 rounds

Williamson St & S Dickinson St

Wider 4-lane urban roadway · existing RRFB + push buttons · visually complex background.

Baseline ≈ 0.5 lux Heights: 10 / 12.5 / 15 ft RRFB present

Milwaukee site map with U-turn test route

Milwaukee · 177 rounds

N Maryland Ave · UWM campus

Two-lane campus roadway · no RRFB or push button · ambient street lighting.

Baseline ≈ 13 lux Heights: 7.5 / 10 / 12.5 ft Lateral: 0 / 9.5 / 16.5 ft

What we varied

Factor	Levels
Lighting spectrum	4000 K · 5000 K · 6500 K · 4 blue configs
Mounting height	3 heights per site
Lateral distance	0 / 9.5 / 16.5 ft (Milwaukee)
Pedestrian target	Adult & child mannequins
Clothing	Dark blue & white
Obstruction	Clear · small vehicle · van parked
Weather / ambient	Clear night · light rain · ± streetlight

Instrumentation

Field hardware: mannequins on skateboards, cameras, GPS, brake logger, lux meter, test vehicles — Field hardware: mannequin skateboards · 4K dual cameras · brake foot switch · lux meter · GPS · two sedans + one van

125 Hz GPSRoadway cameraDriver IR cameraBrake loggerLux meterRemote skateboard control

Drivers were never told when or where the mannequin would cross.

Measured illuminance at the crosswalk (Madison)

≈ 0.5 luxBaseline · no enhanced lighting
≈ 21 luxEnhanced crosswalk lighting
≈ 40 luxEnhanced + floodlight (streetlight sim.)

Lux meter readings: 0.5, 21, and 40 lux — Lux meter readings: (a) 0.5 lux baseline · (b) 21 lux enhanced · (c) 40 lux with floodlight

Nighttime field testing setup at Madison and Milwaukee — Nighttime testing: (a) Madison, wet pavement · (b) Milwaukee, blue-lit crosswalk

Field effort under harsh and tough conditions

All 281 rounds ran at night, including light rain, wet pavement, and late-season cold.

Instrumented test vehicle on wet night street

Wide view of the wet Madison test street at night

How We Measured

Field measurements, eye tracking, and driver-response analysis

A CNN pipeline found the exact frame each driver first recognized the pedestrian, then synchronized it with GPS, speed, and brake records.

Experimental design and synchronized measurements

Controlled mannequin crossings and vehicle approaches compare lighting spectra, installation geometry, and pedestrian and roadway conditions. Roadway video, driver-facing infrared video (30 fps), 125 Hz GPS, brake records, and illuminance measurements capture each encounter. Time alignment connects eye onset with the vehicle trajectory and brake event.

Eye tracking and recognition onset

CNN face landmark localization — (a) CNN face landmarks

Pupil center and gaze vector estimation — (b) Pupil center & gaze vector

Frame-level gaze timeline with eye onset — Frame-level gaze timeline illustrating recognition onset.

Reaction time (RT): Time from first recognition to brake press; shorter indicates faster response.
Detection distance (DD): Vehicle-to-crosswalk distance at first recognition; longer indicates earlier detection.

Conceptual top view of reaction time and detection distance — Conceptual top view: reaction distance + braking distance, all referenced to a fixed crosswalk location

GPS trajectory mapping for the Madison experiment — 125 Hz GPS trajectory mapping: Madison approach path verification

Quality control

Every eye onset was verified against the driver video, the roadway video, and the brake-event timestamp before analysis.

Face detection 95.6% combined 93.8% Milwaukee 98.6% Madison 30 fps IR video · ≈33 ms resolution Blinks, saccades & head pose filtered from noise

Only trials passing synchronization, video, GPS, and brake-match checks entered the final analysis.

Project videos

Field demonstrations and eye-tracking analysis

Milwaukee Demonstration

N Maryland Ave · two-lane campus roadway

Madison Demonstration

Williamson St & S Dickinson St · RRFB site

Eye-Tracking Pipeline

Driver-facing infrared video · onset detection

Main findings

Earlier detection under enhanced illumination

Madison · Blue Baseline

Baseline · RT 0.71 s212 ft

Enhanced · RT 0.67 s275 ft

+63 ft earlier detection · faster reaction

Milwaukee · Ice Blue

Baseline · RT 0.92 s242 ft

Enhanced · RT 0.69 s261 ft

+19 ft earlier detection · RT −0.23 s

In these field experiments, the selected enhanced configurations increased detection distance and reduced reaction time relative to each site’s baseline. The preferred spectrum differed by site: Blue Baseline in Madison and Ice Blue in Milwaukee.

These comparisons describe the tested configurations at two sites. Transfer to other roadways requires review of geometry, illumination coverage, and glare.

Lighting spectrum

Source-reported reaction time (RT, seconds) and detection distance (DD, feet) for every tested spectrum.

Milwaukee · 177 nighttime rounds

Spectrum	RT (s)	DD (ft)
Baseline (no enhanced)	0.92	242.0
4000 K	0.72	237.2
5000 K	0.82	239.4
6500 K	0.75	244.6
Blue Baseline	0.73	256.4
Ice Blue ★	0.69	260.8
Pure Royal Blue	0.83	239.9
Sky Blue	1.13	254.8

Ice Blue: RT 0.69 s and DD 260.8 ft. Blue Baseline exceeded 4000 K by 19.2 ft in detection distance.

Madison · 104 nighttime rounds

Spectrum	RT (s)	DD (ft)
Baseline (no enhanced)	0.71	212.0
4000 K	0.66	241.8
5000 K	0.77	251.3
6500 K	0.94	240.0
Blue Baseline ★	0.67	275.0
Ice Blue	1.20	221.3
Pure Royal Blue	0.62	209.1
Sky Blue	1.13	215.9

Blue Baseline: RT 0.67 s and DD 275.0 ft, 33.2 ft beyond 4000 K and 63 ft beyond baseline.

Milwaukee spectrum performance comparison — Milwaukee spectrum performance: RT & DD

Madison spectrum performance comparison — Madison spectrum performance: RT & DD

Installation geometry and combined configurations

Source-selected configurations: Milwaukee—Ice Blue, 12.5 ft mounting height, 9.5 ft lateral placement; Madison—Blue Baseline, 15.0 ft mounting height. Lateral placement was not independently varied in Madison. Both source recommendations specify no spill control.

Milwaukee lateral distance comparison — Lateral placement: best: 9.5 ft

Milwaukee mounting height comparison — Mounting height: best: 12.5 ft

Madison mounting height comparison — Mounting height: best: 15.0 ft

Milwaukee combined configuration comparison — Combined comparison: spectrum · lateral distance · mounting height

Madison combined spectrum and height comparison — Combined spectrum + height comparison

Pedestrian characteristics, spill control, and obstructions

Milwaukee mannequin type results — Milwaukee · Mannequin type: Adult vs. child differences were small relative to overlapping error bars.

Milwaukee spill control results — Milwaukee · Spill control: Crosswalk-only lighting showed the longest DD; limited trials, reference only.

Milwaukee obstruction results — Milwaukee · Obstruction: A parked vehicle sharply reduced detection distance; the main effect is later recognition.

Madison mannequin type results — Madison · Mannequin type: The child mannequin had the highest RT and shortest DD; drivers recognized the smaller target later.

Madison spill control results — Madison · Spill control: 50% spill control looked favorable but with very few trials; reference only.

Madison obstruction results — Madison · Obstruction: Results varied by condition; drivers may have approached the larger van more cautiously.

Clothing condition effects by lighting spectrum — Clothing effects: Ice Blue best at Milwaukee for both dark & white clothing; Blue Baseline best at Madison

Cross-site comparison

Site-specific spectrum decision rankings — Spectrum ranking: (a) Milwaukee: Ice Blue · (b) Madison: Blue Baseline

Preferred spectra differed by roadway context: Ice Blue in Milwaukee and Blue Baseline in Madison. The source carries Blue Baseline forward for generalized guidance; roadway geometry, coverage, and glare still require site review.

Eye-tracking and visual-response metrics · N = 163

Metric	Baseline	Enhanced	p	Meaning
Pupil diameter	5.31 mm	4.87 mm	<0.001	Pupil constriction under enhanced light
Contrast ratio	0.72	0.88	<0.001	Higher pedestrian–background contrast ✓
Glare index	0.18	0.31	<0.001	Increased: monitor glare in design ⚠
Visual comfort score	3.82	3.41	0.002	Slight comfort reduction
Blink rate	0.31 /s	0.22 /s	<0.001	Reduced blink rate
Pupil asymmetry	0.08	0.13	<0.001	Greater asymmetry; possible glare indicator ⚠
Eye aspect ratio	0.284	0.298	0.041	Slightly higher under enhanced lighting
Saccade velocity	142.3°/s	168.7°/s	<0.001	Faster visual scanning ✓

Enhanced lighting increased contrast and saccade velocity, alongside higher glare index and slightly lower visual comfort. These results support site-specific glare review.

Source-recommended lighting specifications

Application context	Spectrum	Height	Lateral	Power
2-lane residential (Milwaukee-type)	Ice Blue	12.5 ft	9.5 ft	Solar + battery
Wider urban (Madison-type)	Blue Baseline	15.0 ft	Site-specific	Solar + battery
Generalized guidance	Blue Baseline	Width-scaled	Width-scaled	Solar + battery

Design illuminance ≥ 20 lux vertical at the pedestrian plane (≈ 21 lux measured in the field). Source recommendations specify no spill control, with site-specific glare review. Generalized specifications are planning guidance and require engineering verification.

Design Guidelines

From two sites to any Wisconsin crosswalk

A planning-level framework, not a fixed standard. Every site still gets engineering review and nighttime verification.

Roadway geometry scaling for mounting height and lateral placement — Height (a), lateral placement (b) & illumination angle (c) vs. road width. **Example:** 44 ft four-lane roadway → ≈ 16.0 ft height, ≈ 11.0 ft lateral, then verified against pole feasibility, glare, and coverage

Blue Baseline OLS models

Variable	RT	DD
Mounting height	0.038 *	1.452
Lateral distance	−0.004	−1.271
Road width	−0.001	1.395
Vehicle speed	0.012	7.244 **
Child vs. adult	0.106	−34.568
High vs. medium ambient	0.065 **	3.457
R²	0.208	0.451

* p < 0.1 · ** p < 0.05. The DD model (R² = 0.451) is the useful screen; predicted DD compares directly with SSD. Exploratory planning tool only.

Stopping sight distance adequacy across roadway types — SSD adequacy: green: predicted DD > required SSD · red: needs design revision

Stopping sight distance screen

Predicted detection distance must exceed AASHTO-required SSD (2.5 s perception-reaction, f = 0.35, level grade).

Pass School-zone, residential, downtown, urban, most suburban

Marginal High-speed 4-lane divided: verify before advancing

Fail Rural 4-lane · high-speed 6-lane divided: revise design first

Required checks before installation

Photometric coverageVertical illumination Glare reviewBeam direction ADA clearanceClear zone UtilitiesSolar access Battery maintenanceElectrical code Median pole reviewWinter durability

For WisDOT Review

Implementation recommendations

Design element	Recommended direction
Primary spectrum	Blue Baseline (blue-shifted LED; controller RGB R 129.0 · G 420.75 · B 741 on the 0–750 scale) · Ice Blue (R 80 · G 520 · B 750) for narrow two-lane residential contexts
Vertical illuminance	≥ 20 lux at the pedestrian plane (≈ 21 lux measured in the field)
Mounting height	Scale with roadway width (10.6 ft @ 22 ft road → 19.2 ft @ 72 ft road) · verify photometrically
Lateral placement	Scale with roadway width (5.6–13.7 ft) · adjust for poles, glare, coverage
Power source	Solar + battery storage, subject to site feasibility
Safety screening	Predicted detection distance must exceed required SSD for the approach speed

1 · Lighting works

Blue-spectrum lighting reduced RT and increased DD vs. baseline at both sites.

2 · Spectrum alone isn't enough

It must combine with illuminance, contrast, coverage, glare control, and geometry.

3 · Optimal spectrum is site-dependent

Ice Blue for two-lane; Blue Baseline for wider roads and generalized use.

4 · Geometry drives transfer

Scale height and placement with roadway width; never copy between sites.

5 · SSD is the safety screen

Predicted DD must exceed required SSD, or the site needs additional review.

Next steps

Pilot deployments · larger datasets · adaptive dimming · winter validation · glare monitoring · statewide guidance updates.

Feedback

Questions, corrections, and suggestions

Reviewing this study? Send a comment to the research team at UW–Milwaukee. Technical questions, data requests, implementation suggestions, and corrections are all welcome.