How to Use TripRisk
TripRisk shows you the actual fatality risk of your driving route — down to individual road segments — using five years of federal crash data, real-time weather, and time-of-day adjustments. This guide walks you through every feature.
Whether you want to find the safest route for a road trip, check how dangerous a particular highway is, or understand how weather and nighttime driving affect your odds — this is where you start.
Quick Start
Get your first route risk estimate in under a minute.
Enter addresses
Type an origin and destination — or right-click the map to set them.
Compare routes
TripRisk shows Fastest, Safest, and Balanced strategies with per-segment risk coloring.
Drive safer
Pick the route that fits your risk tolerance. The Risk in Perspective widget puts the numbers in context.
Planning a Route
Entering addresses
Type any US address, city name, or landmark into the Origin and Destination fields. TripRisk uses OpenStreetMap's Nominatim geocoder to resolve addresses. You can also type cross-streets like "Colfax and Broadway, Denver".
Right-click shortcut: Right-click anywhere on the map to set the origin or destination directly. A context menu lets you choose which field to fill, or you can add the location as an intermediate stop.
Multi-stop routes
Click + Add stop to add intermediate waypoints. You can drag stops to reorder them. Each leg is routed and risk-scored independently, then combined into a total trip risk.
Round trips
Toggle Round trip to automatically route back to your starting point. Your current destination becomes a stop, and the final leg returns to the origin.
Departure time
Set your departure date and time to enable two adjustments:
- Weather: TripRisk fetches the forecast along your route and applies rain, snow, and fog risk multipliers based on FARS crash data.
- Daylight: Whether you'll be driving during the day, twilight, or night — each with different fatality-rate multipliers.
Vehicle type
Select your vehicle type to adjust fatality probability. Vehicle multipliers are based on IIHS/NHTSA per-mile fatality rates by vehicle category:
| Vehicle | Risk multiplier |
|---|---|
| Large SUV / Pickup | 0.5–0.7x |
| Sedan / Midsize | ~1.0x |
| Small car / Compact | 1.1–1.3x |
| Motorcycle | ~29x |
Motorcycle riders face dramatically higher risk per mile. TripRisk displays a warning when motorcycle is selected.
Understanding Your Results
After computing routes, TripRisk displays several complementary views of your trip's risk profile.
Route summary panel
The panel in the bottom-left corner shows all three route strategies with their distance, duration, and fatality probability. Click a strategy to highlight its route on the map. The active route is shown with a bold outline.
Risk strip
The horizontal bar below the header shows per-segment risk as a color gradient along the length of your route. Green segments are safer, yellow is moderate, and red indicates the highest fatality rates. Hover over any point to see the risk value and the corresponding location highlights on the map.
The strip also shows weather icons at sample points along the route, and a daylight indicator (sun, sunset, or moon) based on your departure time.
Map colors
The route overlay on the map uses the same green-to-red color scale as the risk strip. Each road segment is colored by its fatality rate, so you can see exactly which stretches of road are most dangerous. The active route is drawn with a thicker line; other strategies appear as thinner, semi-transparent alternatives.
Risk in Perspective
The widget in the bottom-right corner compares your trip's fatality probability to familiar risks — from lightning strikes and shark attacks to house fires and falls. This puts the raw numbers in context: a "1 in 3.4 million" probability is roughly as likely as being struck by lightning this year.
Route Strategies
TripRisk computes three route options, each optimizing a different objective.
Fastest
Minimizes travel time using A* search. This is equivalent to what Google Maps or Apple Maps would give you. Risk is displayed but not optimized.
Safest
Minimizes fatality probability using bidirectional Dijkstra on risk-weighted edges. May take longer than the fastest route, but routes through roads with the lowest per-mile fatality rates.
Balanced
Finds the safest route within 25% of the fastest travel time using Lagrangian optimization. This is usually the best practical choice — significantly safer than fastest, with minimal time penalty.
Note: For many trips — especially those that primarily use interstate highways — all three strategies may return similar or identical routes. This is because interstates genuinely have the lowest fatality rate per vehicle-mile traveled. The safest route is the fastest route when the highway is both the quickest and least dangerous option.
For a full explanation of the routing algorithms and risk formulation, see Methodology: Route Optimization.
Weather & Time of Day
Set a departure time in the route planner to enable weather and daylight adjustments. These multiply your base fatality probability — they don't change the route itself, only the risk estimate.
Weather multipliers
TripRisk samples weather conditions every 10 km along the fastest route using Open-Meteo forecasts, then applies risk multipliers derived from FARS crash data by road category:
| Condition | Risk multiplier |
|---|---|
| Clear / Dry | 1.0x (baseline) |
| Rain | 1.1–1.6x |
| Snow / Ice | 1.6–3.7x |
| Fog | 1.2–1.8x |
Ranges reflect variation across road categories (interstates vs. local roads). Multipliers are derived from FARS weather-related crash frequencies adjusted for exposure time, not the raw 78/17/3/2% weather occurrence split.
Time of day
Fatal crash rates are dramatically higher at night. TripRisk uses astronomical sunrise/sunset calculations for your route's location and classifies conditions as day, twilight, or night:
| Condition | Raw risk ratio | Adjusted multiplier |
|---|---|---|
| Day | 1.0x | ~0.70x |
| Twilight | 1.5x | ~1.05x |
| Night | 2.75x | ~1.93x |
"Adjusted multiplier" accounts for the fact that HPMS base rates already include an average mix of day/night driving (70% day, 8% twilight, 22% night). The adjustment removes this baked-in average before applying the specific condition.
Best time to drive: Daytime driving is the safest. If you have flexibility, leaving in the morning reduces your fatality risk by roughly 2.75x compared to the same trip at midnight. The risk strip shows a sun, sunset, or moon icon to reflect your departure-time conditions.
Road Safety Explorer
The Road Safety Explorer lets you browse a nationwide heatmap of road danger without planning a specific route. Use it to investigate roads in your area, compare highways, or find the most dangerous stretches near you.
Loading road data
Zoom into any area and click Load Road Data (or enable auto-load in settings). The map fetches HPMS road segments for the visible area and colors them by fatality rate. Data loads progressively — you can pan and zoom while more segments appear.
Reading the heatmap
Road colors indicate fatality rate per 100 million vehicle-miles traveled (VMT):
Click any road segment to see its details: road name, functional class, AADT (traffic volume), fatality rate, and number of fatal crashes recorded.
Crash markers
Toggle Show crashes in settings to display skull icons at the locations of actual fatal crashes from FARS data. Each marker shows the year, number of fatalities, and contributing factors when clicked.
Explorer settings
Click the gear icon to access settings: toggle auto-load, show/hide crash markers, adjust road opacity, and filter by road functional class (interstate, arterial, collector, local).
Frequently Asked Questions
Common questions about driving safety and how TripRisk works.