Night Pedestrian Fatality: Rain, Sodium Light and Class D Airspace
At 22:40 a 52-year-old pedestrian is struck by a pickup on a two-lane rural road with a 45 mph limit. The victim was pronounced at the scene and has been removed. Debris, including a broken headlight lens, a side mirror, a shoe and 60 m of scattered glass, lies across both lanes. The road surface is wet from earlier rain and light rain is now falling; the nearest streetlight is a sodium lamp 40 m away. Ambient temperature is 9 °C. The tow truck is 20 minutes out and the road must reopen by 05:00. Your equipment includes a DSLR with a speedlight, a tripod, a total station with a six-hour battery, a department drone whose Part 107 pilot is off duty, and a GPS-enabled tablet. The incident is 3.2 km from a Class D airport. The detective wants GPS coordinates for every debris item and photographs that show the scene the way the driver would have seen it.
1. Give your photo plan: exposure and lighting decisions, shooting order, and how you handle the rain and the driver's-view request.
Read the worked answer
Order first Photograph the as-found condition before you place cones, markers or additional lights. Overall views from four corners, then a mid-range pass, then close-ups of each debris item with a scale. Add a video walk-through at the start and, if time allows, at the end.
Exposure and lighting
- Tripod, manual mode, remote or timer release. Start around ISO 800, f/8, and test exposures; the sodium light is a strong color cast, so set white balance deliberately and record it.
- Use a flashlight to paint light across the scene during a long exposure for even illumination, and take a separate ambient-only frame. Keep both: one shows what the eye could see, the other shows detail.
- Do not fire the speedlight directly into falling rain; backscatter creates white streaks across the frame. Angle it, or use the paint method instead.
- Lens hood and umbrella; wipe the front element between frames and note the rain in the log.
Driver's-view request Shoot from roughly driver eye height at measured distances, using a reference to show the sequence. Then state the limitation plainly in the report: you cannot reproduce headlight illumination, approach speed, windshield condition or the driver's own vision. The photographs show geometry and sight lines, not perception.
Rain Photograph the wet road surface and note the rain intensity and time. If the rain changes, shoot a repeat set so the change is documented rather than discovered at trial.
2. Choose the mapping method and justify it. Address the tablet GPS and the Class D airport constraint.
Read the worked answer
Total station is the defensible choice Set a datum and at least two reference points that will survive the night, then shoot the debris field, the final rest positions, the road edges and the site lines. The instrument, its calibration and its operator go in the notes. Battery life is the limit, so plan the shot list and prioritize the debris field and the impact and rest points.
Tablet GPS Consumer GPS is roughly 3 to 5 m accurate at best and drifts with conditions. That is fine for orienting a sketch index or labeling a photo location, and inappropriate for debris coordinates you will defend. If you use it, label the values as approximate.
Drone The site is 3.2 km from a Class D airport, so flight requires a Part 107 remote pilot and airspace authorization through LAANC or a waiver. The pilot is off duty, it is night, and it is raining at 9 °C. Even with authorization, rain and wind may exceed the aircraft's limits, and night operations need the anti-collision lighting and a pilot current for night work. The realistic answer is no flight tonight; document the decision and the reason rather than improvising.
If the total station fails Fall back to a measured baseline with a tape and offsets to each item, recorded in a field sketch that is later digitized. A taped baseline with clear reference points is still defensible if it is documented.
3. The tow truck is 20 minutes out and the road must reopen by 05:00. What is your sequence, and which documentation gaps must not be left?
Read the worked answer
Sequence
- Photographs, as-found, before anything is added or moved.
- Measurements of the debris field, impact area and final rest positions.
- Mark the vehicle's tire positions with paint before the tow.
- Photograph the vehicle damage, the undercarriage and the contact points; collect the lens and mirror fragments and check for a match.
- Collect the debris, package, seal and log it.
- Release to the tow.
Gaps that cannot be left
- Vehicle final rest position and orientation, and the tire marks or paint marks that prove it.
- Debris field extent, especially the 60 m of glass, with measurements and a sketch.
- Road surface condition: wet, rain intensity and the time, plus repeat photographs if the rain changes.
- The shoe and where it was relative to the debris and the rest position.
- Any evidence that traffic or the tow destroys, documented before release.
- A written note of the reopen decision, who made it and when.
Deadline management 05:00 is achievable if you do not let the tow truck in before step 4 and if you do not spend battery on low-value measurements. If it slips, communicate early to the watch commander and explain what would be lost by truncating. 'We can open at 04:45 with these three items unmeasured' is a professional statement; discovering the gap at trial is not.