---
slug: how-much-deadlier-30-than-20
passed: 2026-10-14
by: the assay line (research/assay-line/cited-1014b/), Codex fixer directed by claude-assaying-boyle-1014; source record by Codex, checked by Codex
checked: 80
confirmed: 59
wrong: 20
unverifiable: 0
observed: 0
stale: 1
---

This was the directed correction pass for this layer at 41fdb2b77b, following the 2026-10-14 cited-1014b triage. The fixer re-read the evidence for all 22 items, applied the supported fixes, retained the six listed MINOR items, and rejected X9 with the location comparison checked numerically. The 58 CONFIRMED claims from N2-codex.md are carried forward below with that checker's source-reading provenance; this is not a new full audit of the 152-entry N2 record. The totals count 13 WRONG and 7 MINOR lines under wrong, 59 CONFIRMED lines including X9, and one STALE metadata field. Five dated correction lines cover the five substantive errors; the obsolete link is a MINOR fix without its own line.

## Claims

- WRONG | [X1] fitted to NHTSA crash reconstructions of 552 struck pedestrians. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | Re-read Tefft 2011, Methods, Data, printed p. 3: 549 input records, 126 excluded for age below 15, one excluded for unknown injury severity, leaving 422 aged 15 or older struck by a single forward-moving car or light truck. Corrected the lead and all layer documentation copies.
- WRONG | [X2] withdrawn by the DfT in 2011 | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | Re-read Road Safety GB: the report dated 17 September 2010 records an existing DfT acknowledgment of overstated campaign risks. Replaced the 2011 withdrawal claim with that documented acknowledgment; no formal withdrawal date is asserted.
- WRONG | [X3] "9 in 10 dead at 40" was officially withdrawn in 2011 | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | The source reports the campaign claim as "an 80% chance of death" at 40 mph and dates its report to 17 September 2010. Replaced the invented 90% quotation and the 2011 withdrawal wording with the source wording and documented acknowledgment.
- WRONG | [X4] In 2011 the Department for Transport, through road safety minister Mike Penning, publicly retracted them | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | The source identifies Mike Penning as road safety minister and reports the acknowledgment on 17 September 2010. Kept the supported attribution and corrected the date and description of the event.
- WRONG | [X5] "misleading statistics only serve to undermine our case." | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | Re-read the source quotation: its ending includes a comma and "not help it." Restored the omitted words and punctuation, rather than silently paraphrasing the quotation.
- WRONG | [X6] The revised figures trace to Rosen and Sander (2009). | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | Re-read Richards 2010, Table 4.1, printed p. 25: British OTS and police fatal file (all ages) gives 7%/31% at 30/40 mph; GIDAS (ages 15+) gives 7%/25%. Corrected the British attribution and cited the table.
- MINOR | [X7] Alert 0.67 s, Typical 1.0 s, Distracted 1.5 s | https://visualexpert.com/Resources/reactiontime.html | Re-read the working www.visualexpert.com version: its expected/unexpected/surprise categories use about 0.7/1.25/1.5 s. They do not establish the page's exact named presets as measured driver states. The triage lists this as loose labelling of illustrative choices at tier C, not evidence that the times are impossible; left unchanged.
- MINOR | [X8] a texting 1.5 s | https://visualexpert.com/Resources/reactiontime.html | Re-read the same reaction-time source: 1.5 s refers to a surprise side incursion, not a texting experiment. The triage treats this as loose wording for an illustrative preset; X9 is true, so the same-sentence WRONG exception does not apply. Left unchanged at tier C.
- CONFIRMED | [X9] the 30 mph car has not touched the brake where the 20 mph car has fully stopped | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | Rejected the finding after re-evaluating the page equations. With reaction time 1.5 s and deceleration 6.6 m/s^2, the 20 mph car stops at 19.467101867 m, before the 30 mph car's braking point at 20.1168 m. The claim compares those locations, not the unchanged pedestrian line at 15 m. At 15 m the slower car strikes at 17.1772 mph, but that does not refute the stated spatial relation. Preserved the sentence.
- MINOR | [X10] The check: every number recomputed in front of you | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | Re-read and executed the surface handler with a Node VM and DOM stand-ins: wet changes the impact readout to 29 mph but leaves the transcript at a=6.60 m/s^2. The triage classifies this every-number checking overclaim as MINOR and requires listing at tier C. Left the heading and handler unchanged.
- MINOR | [X11] For your current settings the page recomputes the fit, the ratio and the stopping coupling | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | Re-read and executed wet, reaction and reset handlers: the calculation transcript retains preceding surface or reaction settings after wet/reset. The triage classifies this checking-completeness overclaim as MINOR and requires listing at tier C. Left the sentence and handlers unchanged.
- WRONG | [X12] fitted to their two published points | https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | Re-read Rosen and Sander equation (2), preprint p. 6, and Table 6, p. 8. The German curve now uses intercept -6.9 and slope 0.090 per km/h, converted to 0.14484096 per mph. Removed the claim that it was a fit through two published anchors. The 1970s ghost is explicitly illustrative.
- MINOR | [X13] driven by country, era, car fleet, medical care | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | Re-read Richards section 4.1, printed p. 23: car design and medical care are possible explanations, with caution about small samples and confidence intervals, not an established decomposition of the US/German difference. The triage lists the overstatement as MINOR at tier C; this sentence is separate from the corrected anchor provenance. Left unchanged.
- WRONG | [X14] fits to each study's published anchor points | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | Corrected model scope to distinguish the Tefft anchor fit, Rosen and Sander's published equation (2), and the illustrative historical ghost. The previous German anchors included the British 31% figure from Richards Table 4.1.
- WRONG | [X15] 552 pedestrians | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | The footer repeated the same false count as X1. Tefft's analysed sample is 422 pedestrians aged 15 or older struck by a single forward-moving car or light truck; corrected the footer and README.
- MINOR | [X16] report PDF mirrored at AAA and NACTO | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://aaafoundation.org/wp-content/uploads/2018/02/2011PedestrianRiskVsSpeedReport.pdf | The old AAA 2018/02 URL returns HTTP 404. Re-opened the working AAA 2026/02 PDF and the NACTO mirror. Updated the AAA link in the footer and layer README; kept NACTO. The triage permits this MINOR fix in the same source sentence as X15, without a correction line of its own.
- MINOR | [X17] Every number recomputes in front of you and is checked against the study's own published anchor points. | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | Re-read the markdown dek and meta description and executed the wet handler: the transcript retains dry deceleration while impacts update. The source audit also checks only five baseline Tefft anchors. The triage requires listing this checking overclaim as MINOR at tier C; left this sentence unchanged in both copies.
- WRONG | [X18] officially withdrawn by the Department for Transport in 2011. | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | The JSON-LD repeated the unsupported 2011 formal-withdrawal chronology. Replaced it with the acknowledgment reported by Road Safety GB on 17 September 2010 and the actual 80% campaign figure.
- STALE | [X19] "dateModified":"2026-07-17" | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | The original dateModified matches the publication date, but git log records later page changes on 2026-09-28 and 2026-10-01. Updated dateModified to this revision date, 2026-10-14. The user's explicit JSON-LD exception needs no separate Updated line; the Corrected lines date this revision.
- WRONG | [X20] the 20 mph car strikes at 0 mph (about 1% risk) | git show 41fdb2b77b:public/strata/how-much-deadlier-30-than-20/index.html; research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | Reproduced the default served script: residual speed is zero and stopping distance is 14.996701867 m before the 15 m pedestrian line, yet the old summary rounded pTefft(0)=0.77138% to 1%. The old impact label and self-check also used the nonzero curve intercept. Added a clean-stop risk guard to accessible text, visible readouts, impact annotations, calculation text and checks; only zero residual counts as no contact. A positive residual below 0.5 mph still reports impact risk.
- WRONG | [X21] "Rosen 2009 (Germany)" / "31.0%" | https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | Evaluated Rosen and Sander equation (2) directly: at 20/30/40/50 mph it gives 1.793011/7.210661/24.854982/58.468792%. The corrected shared model now renders 1.8%/7.2%/24.9%/58.5% and a 4.0x 30-to-20 ratio in the German table. The old cells were 1.2%/7.0%/31.0%/72.8%.
- WRONG | [X22] (added) withdrawn by DfT 2011 | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | Replaced the canvas label with "DfT: overstated (2010)" after re-reading the dated Road Safety GB report. The verifier now checks that acknowledgment label rather than requiring the false 2011 withdrawal claim.
- CONFIRMED | The Ten Miles an Hour That Triple the Odds | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [title] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | Hit a person walking at 20 mph and, on the US average curve, about 1 in 14 are killed. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [lead-20] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | At 30 mph it is about 1 in 5. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [lead-30] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | That is roughly triple the odds for ten more miles an hour | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [lead-odds] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | Its average risk of death passes through 10% at 23 mph, 25% at 32 mph, 50% at 42 mph, 75% at 50 mph and 90% at 58 mph. | https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ | N2 source re-read carried forward: [death-anchors] AAA states "10% at an impact speed of 23 mph, 25% at 32 mph, 50% at 42 mph, 75% at 50 mph, and 90% at 58 mph."
- CONFIRMED | Tefft is the US average (solid). | https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ | N2 source re-read carried forward: [tefft-us] The methods say "Risks were standardized to represent the average risk for a pedestrian struck by a car or light truck in the United States in years 2007" followed by 2009. This is the study population average, not a current nationwide census.
- CONFIRMED | Rosen is German data (dashed, lower). | https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf | N2 source re-read carried forward: [rosen-german] The primary paper says "We queried the German In-Depth Accident Study (GIDAS)" and describes years 1999 to 2007. Its equation gives lower risk than the US average over the 20-40 mph comparison band. The separately reported error concerns the page implementation of that curve.
- CONFIRMED | on the US average adult curve it is about 2.7x (7.3% to 20.0%) | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [caveat-average] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | edging up toward 3x for older pedestrians, whose curve is steeper (a 70-year-old runs about 2.9x, from roughly 13% to 37%) | https://www.propublica.org/article/unsafe-at-many-speeds; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [caveat-older] The record excerpt gives only 40 mph age comparisons, not the claimed 20-to-30 ratio. The disclosed approximation independently yields 13.0% to 37.1%, ratio 2.856; Streetsblog reports 87% survival at 20 mph for age 70, and ProPublica reports 70% death at 40. Scope this to the stated approximate model.
- CONFIRMED | studies disagree on the absolute number by two to three times. | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf; https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [study-disagreement] Richards Table 4.1 prints "GIDAS (Rosén and Sander) (ages 15+)" with 7 and 25 at 30 and 40 mph. Tefft gives 20% at 30. Thus the two-to-three-fold comparison is supported at 30 mph, the question being answered; it is not a constant multiplier across speeds.
- CONFIRMED | Switch the study to Rosen 2009 and 30 mph drops to about 7 percent. | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf; https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [rosen-seven] Richards Table 4.1 prints "GIDAS (Rosén and Sander) (ages 15+)" with 7 and 25 at 30 and 40 mph. Tefft gives 20% at 30. Thus the two-to-three-fold comparison is supported at 30 mph, the question being answered; it is not a constant multiplier across speeds.
- CONFIRMED | What is robust across every modern study is the shape (steep, nonlinear) and the direction and rough size of the 20-versus-30 gap. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json | N2 source re-read carried forward: [robust-all-studies] Tefft says "The shape of the curve relating risk of death to impact speed in the current study was very similar to that of Rosén & Sander." The review reports monotonic increases throughout. The page baseline logistic and the actual Rosen equation are convex on 20-40 mph, and the US fit has risk ratio 2.743. Read "rough size" qualitatively, not as an identical ratio in every study.
- CONFIRMED | The UK THINK! / "Kill Your Speed" campaign | https://www.think.gov.uk/about-think/story-of-think/; https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | N2 source re-read carried forward: [campaign-name] The official timeline says "Kill Your Speed campaign also launches." RSGB names "The Think! campaign". The page distinguishes the campaign from the 1970s data behind its figures.
- CONFIRMED | told a generation that a pedestrian had a 20% chance of death at 30 mph and about 80 to 85% at 40 mph. | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | N2 source re-read carried forward: [campaign-old-risks] RSGB gives "20% chance of being killed" at 30 mph and "80% chance of death" at 40, within the page stated 80-85% range; it says the figures "were based on 1970s data" and overestimated risk. The page numerical ghost specifically choosing 85% is illustrative.
- CONFIRMED | Those numbers were built on 1970s crash data and badly overstated the high-speed risk. | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | N2 source re-read carried forward: [old-data-and-overstatement] RSGB gives "20% chance of being killed" at 30 mph and "80% chance of death" at 40, within the page stated 80-85% range; it says the figures "were based on 1970s data" and overestimated risk. The page numerical ghost specifically choosing 85% is illustrative.
- CONFIRMED | stating that the modern probability of death is about 7% at 30 mph and 31% at 40 mph | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/; https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | N2 source re-read carried forward: [retraction-modern-risks] RSGB prints "7% at 30mph and 31% at 40mph". It attributes these numbers to the report of latest research, then quotes Penning welcoming release of the data. The rates are reported correctly; their German attribution elsewhere is wrong.
- CONFIRMED | 30 mph really is markedly (roughly triple) deadlier than 20 mph | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [triple-restated] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | the graphic your driving instructor showed you was retired over a decade ago. | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | N2 source re-read carried forward: [instructor-retirement] The 2010 report, including the contemporaneous RSGB officer comment "removed all reference to the old figures", supports retirement more than a decade before the page date in 2026. The generic instructor address is rhetorical, not an identifiable person claim.
- CONFIRMED | The studies disagree on the absolute risk, not the direction. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json | N2 source re-read carried forward: [studies-agree-direction] Tefft says "The shape of the curve relating risk of death to impact speed in the current study was very similar to that of Rosén & Sander." The review reports monotonic increases throughout. The page baseline logistic and the actual Rosen equation are convex on 20-40 mph, and the US fit has risk ratio 2.743. Read "rough size" qualitatively, not as an identical ratio in every study.
- CONFIRMED | Fatality curves are indexed to impact speed, the speed at the moment of contact, which is lower than travel speed whenever any braking happened. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [impact-versus-travel] Tefft states "risk of severe injury and risk of death in relation to impact speed". Deceleration before contact reduces speed by the disclosed kinematic equations; this is correctly conditional on braking.
- CONFIRMED | the 30 mph car is deadlier not only per impact but because it is far more likely to strike at speed at all. | https://visualexpert.com/Resources/reactiontime.html; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [faster-strikes] The cited stopping discussion separates "Reaction Distance" and "Physical Force Distance". Independently, d=v*t+v^2/(2a) gives 14.9967 m for 20 mph versus 27.0370 m for 30 mph at t=1 and a=6.6, so the 15 m scenario has only the faster car striking. These are conditional kinematic comparisons, not a measured crash-frequency estimate.
- CONFIRMED | From one shared point where the driver first sees the pedestrian, the slower car can often stop clean while the faster car has barely begun braking. | https://visualexpert.com/Resources/reactiontime.html; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [shared-sight-line] The cited stopping discussion separates "Reaction Distance" and "Physical Force Distance". Independently, d=v*t+v^2/(2a) gives 14.9967 m for 20 mph versus 27.0370 m for 30 mph at t=1 and a=6.6, so the 15 m scenario has only the faster car striking. These are conditional kinematic comparisons, not a measured crash-frequency estimate.
- CONFIRMED | energy scales with speed squared | https://www.grc.nasa.gov/WWW/K-12/airplane/thermo1f.html | N2 source re-read carried forward: [energy-squared] NASA gives "K = (m * u^2) / 2". For the same mass, (30/20)^2 = 2.25 exactly. The equal-mass condition is implicit in the page speed-only comparison.
- CONFIRMED | AASHTO design 2.5 s | https://www.fhwa.dot.gov/publications/research/safety/15030/002.cfm | N2 source re-read carried forward: [aashto-detent] FHWA says "The currently recommended design is a perception-reaction time of 2.5 s." The surrounding text links the design criterion to the AASHTO reference.
- CONFIRMED | Tefft's injury curve sits well to the left: 50% severe injury at 31 mph versus 50% death at 42 mph | https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ | N2 source re-read carried forward: [injury-versus-death] AAA gives severe-injury "50% at 31 mph" and death "50% at 42 mph".
- CONFIRMED | a 70-year-old at about 13% at 20 mph | https://sf.streetsblog.org/2016/05/31/3-graphs-that-explain-why-20-mph-should-be-the-limit-on-city-streets | N2 source re-read carried forward: [propublica-age-reads] The supplied Streetsblog passage says the age-70 survival chance at 20 mph is "87 percent", hence 13% death. It is a secondary read of ProPublica, accurately identified by its URL.
- CONFIRMED | 70% at 40 mph | https://www.propublica.org/article/unsafe-at-many-speeds | N2 source re-read carried forward: [propublica-age-70-at-40] ProPublica says "A 30-year-old has a 36 percent chance of dying" and gives age 70 as "70 percent" at 40 mph. It says Tefft "sent me the data from his 2011 report".
- CONFIRMED | a 30-year-old's 36% at 40 mph | https://www.propublica.org/article/unsafe-at-many-speeds | N2 source re-read carried forward: [propublica-younger-read] ProPublica says "A 30-year-old has a 36 percent chance of dying" and gives age 70 as "70 percent" at 40 mph. It says Tefft "sent me the data from his 2011 report".
- CONFIRMED | All fatality curves are fit to crashes that were recorded, and faster crashes are likelier to be reported and reconstructed, which can bias the absolute risks upward (Rosen 2011 addresses this). | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf | N2 source re-read carried forward: [recording-bias] The review says "papers written before 2000" had "a large bias towards severe and fatal injuries" and "The consequence was to overestimate the fatality risks." PubMed itself returned a challenge; the same article abstract was opened through Europe PMC. Rosen 2009 also explains why injury-based sampling and nonreporting affect estimates.
- CONFIRMED | A pedestrian's risk of death rises steeply and nonlinearly with impact speed, and the curve is convex through the 20 to 40 mph band, so the gap from 20 to 30 mph is larger than the gap from 10 to 20 mph. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json | N2 source re-read carried forward: [convex-20-40] Tefft says "The shape of the curve relating risk of death to impact speed in the current study was very similar to that of Rosén & Sander." The review reports monotonic increases throughout. The page baseline logistic and the actual Rosen equation are convex on 20-40 mph, and the US fit has risk ratio 2.743. Read "rough size" qualitatively, not as an identical ratio in every study.
- CONFIRMED | The direction and rough size of the 20-versus-30 gap (roughly triple on the US average adult curve) is stable. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf; https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json | N2 source re-read carried forward: [gap-stable] Tefft says "The shape of the curve relating risk of death to impact speed in the current study was very similar to that of Rosén & Sander." The review reports monotonic increases throughout. The page baseline logistic and the actual Rosen equation are convex on 20-40 mph, and the US fit has risk ratio 2.743. Read "rough size" qualitatively, not as an identical ratio in every study.
- CONFIRMED | Kinetic energy scales with the square of speed, so 30 mph carries (30/20)2 = 2.25 times the energy of 20 mph. | https://www.grc.nasa.gov/WWW/K-12/airplane/thermo1f.html | N2 source re-read carried forward: [energy-225] NASA gives "K = (m * u^2) / 2". For the same mass, (30/20)^2 = 2.25 exactly. The equal-mass condition is implicit in the page speed-only comparison.
- CONFIRMED | Reaction distance is linear in speed and braking distance is quadratic, so from a shared sight line the faster car is much more likely to still be moving when it reaches the pedestrian. | https://visualexpert.com/Resources/reactiontime.html; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [reaction-linear-braking-quadratic] The cited stopping discussion separates "Reaction Distance" and "Physical Force Distance". Independently, d=v*t+v^2/(2a) gives 14.9967 m for 20 mph versus 27.0370 m for 30 mph at t=1 and a=6.6, so the 15 m scenario has only the faster car striking. These are conditional kinematic comparisons, not a measured crash-frequency estimate.
- CONFIRMED | The absolute probability of death at a given speed is contested: the US PCDS curve (Tefft) says about 20% at 30 mph, the German GIDAS curve (Rosen and Sander) says nearer 7 to 10% | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf; https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [us20-vs-de7] Richards Table 4.1 prints "GIDAS (Rosén and Sander) (ages 15+)" with 7 and 25 at 30 and 40 mph. Tefft gives 20% at 30. Thus the two-to-three-fold comparison is supported at 30 mph, the question being answered; it is not a constant multiplier across speeds.
- CONFIRMED | B. C. Tefft, "Impact Speed and a Pedestrian's Risk of Severe Injury or Death" (AAA Foundation for Traffic Safety, September 2011 | https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/; https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [tefft-report-citation] The AAA citation names "Tefft, B.C. (2011)" and the report. The PDF cover identifies September 2011 and the author page gives "Brian C. Tefft".
- CONFIRMED | B. C. Tefft, "Impact Speed and a Pedestrian's Risk of Severe Injury or Death" (AAA Foundation for Traffic Safety, September 2011; also Accident Analysis & Prevention 50:871-878, 2013) | https://api.crossref.org/works/10.1016/j.aap.2012.07.022 | N2 source re-read carried forward: [tefft-journal-citation] Crossref names Brian C. Tefft, issued January 2013, volume 50, pages "871-878", and the matching title. The separately published technical report is September 2011.
- CONFIRMED | E. Rosen & U. Sander, "Pedestrian fatality risk as a function of car impact speed" (Accident Analysis & Prevention 41(3):536-542, 2009 | https://api.crossref.org/works/10.1016/j.aap.2009.02.002 | N2 source re-read carried forward: [rosen-citation] Crossref names Erik Rosén and Ulrich Sander, May 2009, volume 41 issue 3, pages "536-542", with the matching title. The author PDF independently agrees.
- CONFIRMED | E. Rosen, H. Stigson & U. Sander, "Literature review of pedestrian fatality risk as a function of car impact speed" (AAP 43(1):25-33, 2011). | https://api.crossref.org/works/10.1016/j.aap.2010.04.003 | N2 source re-read carried forward: [review-citation] Crossref names Erik Rosén, Helena Stigson and Ulrich Sander, January 2011, volume 43 issue 1, pages "25-33", with the matching review title.
- CONFIRMED | from NHTSA's Pedestrian Crash Data Study, crash years 1994-1998 | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [pcds-origin-dates] Tefft says the NASS Pedestrian Crash Data Study compiled investigations "from July 1994 through December 1998".
- CONFIRMED | Average risk of death: 10% @23, 25% @32, 50% @42, 75% @50, 90% @58 mph. | https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ | N2 source re-read carried forward: [footer-anchors] AAA states "10% at an impact speed of 23 mph, 25% at 32 mph, 50% at 42 mph, 75% at 50 mph, and 90% at 58 mph."
- CONFIRMED | author copy at NACTO | https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf | N2 source re-read carried forward: [rosen-author-copy] The NACTO PDF begins "Preprint of article published in Accident Analysis and Prevention 41 (2009)" and names Rosén and Sander.
- CONFIRMED | German GIDAS 1999-2007, 490 cases. | https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf | N2 source re-read carried forward: [gidas-dates-cases] The primary paper says "years 1999 to 2007" and "sample consisted of 490 pedestrians aged 15 to 96 years" after exclusions.
- CONFIRMED | Selection bias in older, steeper curves: | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21094293%20AND%20SRC:MED&resultType=core&format=json; https://nacto.org/wp-content/uploads/pedestrian_fatality_risk_function_car_impact_speed_rosen.pdf | N2 source re-read carried forward: [review-selection-bias] The review says "papers written before 2000" had "a large bias towards severe and fatal injuries" and "The consequence was to overestimate the fatality risks." PubMed itself returned a challenge; the same article abstract was opened through Europe PMC. Rosen 2009 also explains why injury-based sampling and nonreporting affect estimates.
- CONFIRMED | Road Safety GB, "THINK! speed campaign exaggerated risks" | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/ | N2 source re-read carried forward: [retraction-citation] The source headline is "THINK! speed campaign ‘exaggerated risks’" at Road Safety GB. Removing decorative quotation marks in the link label does not change the identification.
- CONFIRMED | DfT / Mike Penning: modern probability of death "7% at 30mph and 31% at 40mph" | https://roadsafetygb.org.uk/news/think-speed-campaign-exaggerated-risks-1191/; https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf | N2 source re-read carried forward: [minister-risk-quote] RSGB prints "7% at 30mph and 31% at 40mph". It attributes these numbers to the report of latest research, then quotes Penning welcoming release of the data. The rates are reported correctly; their German attribution elsewhere is wrong.
- CONFIRMED | ProPublica, "Unsafe at Many Speeds" (2016) | https://www.propublica.org/article/unsafe-at-many-speeds | N2 source re-read carried forward: [propublica-citation] The page is titled "Unsafe at Many Speeds", by Lena V. Groeger, dated "May 25, 2016".
- CONFIRMED | built on Tefft's model (30 yr about 36% versus 70 yr about 70% at 40 mph). | https://www.propublica.org/article/unsafe-at-many-speeds | N2 source re-read carried forward: [propublica-based-on-tefft] ProPublica says "A 30-year-old has a 36 percent chance of dying" and gives age 70 as "70 percent" at 40 mph. It says Tefft "sent me the data from his 2011 report".
- CONFIRMED | This layer's check reads the bytes this page serves and asserts against them. | git show 58f60be9ab:research/how-much-deadlier-30-than-20/verify-how-much-deadlier-30-than-20.mjs | N2 source re-read carried forward: [placard-reads-bytes] The verifier calls fs.readFileSync on the served page and checks the withdrawal label and a regex around 85%. Literal file coupling is confirmed by the control mutation failing. It does not check headline values; the HIGH finding in research/assay-line/cited-1014b/how-much-deadlier-30-than-20/N2-codex.md:218 records that distinct limitation in the pinned verifier.
- CONFIRMED | A pedestrian struck at 30 mph is killed roughly three times as often as one struck at 20 mph. | https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [dek-triple] The report says "one in five (20%) die" at 30 mph. Its anchors, independently refitted, give 7.2821% at 20 and 19.9774% at 30: risk ratio 2.74335; odds ratio 3.17857. Both round to roughly triple. The record excerpt alone omits 20 mph; the disclosed page fit supplies it.
- CONFIRMED | The German GIDAS curve (Rosen and Sander 2009) puts the absolute risk two to three times lower, so studies disagree on the number while agreeing the curve is steep. | https://ukr-resources-4.s3.eu-west-2.amazonaws.com/wp-content/uploads/2018/12/08181404/Relationship_between_Speed_and.pdf; https://aaafoundation.org/wp-content/uploads/2026/02/2011PedestrianRiskVsSpeedReport.pdf | N2 source re-read carried forward: [metadata-german-lower] Richards Table 4.1 prints "GIDAS (Rosén and Sander) (ages 15+)" with 7 and 25 at 30 and 40 mph. Tefft gives 20% at 30. Thus the two-to-three-fold comparison is supported at 30 mph, the question being answered; it is not a constant multiplier across speeds.
- CONFIRMED | That page shows total stopping distance is reaction (linear in v) plus braking (quadratic in v); this one feeds the residual speed at the pedestrian back into the fatality curve, so the slower car stops clean while the faster one is still doing about 28 mph and that speed sets the odds of death. | git show 58f60be9ab:public/strata/why-stopping-distance-quadruples/index.html; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [related-stop] The linked pinned page labels reaction "linear" and braking "quadratic" and gives total stop as their sum; this layer default coupling separately recreates 28.1968 mph.
- CONFIRMED | that page flips the fear from flying to driving per mile, this one shows the 20-to-30 mph gap is roughly triple while naming which study and which age nudge the multiple upward. | git show 58f60be9ab:public/strata/the-trip-that-flips-the-fear/index.html | N2 source re-read carried forward: [related-flying] The linked page says "Per mile, flying is untouchable" and compares flying and driving rates. This entry describes that page framing; it is not a new independent verification of every number on that separate layer.
- CONFIRMED | that page shows braking distance is set by tire grip so all-wheel drive does not stop shorter, and this page uses the same reaction-plus-braking integration to decide whether the car reaches the pedestrian still moving. | git show 58f60be9ab:public/strata/does-awd-help-in-snow/index.html | N2 source re-read carried forward: [related-awd] The linked page gives braking distance d=v^2/(2*mu*g) and same-grip comparisons independent of driven wheels. The source record description accurately describes the linked model.
- CONFIRMED | an axle running out of its friction circle there, a constant braking force burning off speed before impact here. | git show 58f60be9ab:public/strata/understeer-vs-oversteer/index.html; git show 58f60be9ab:public/strata/how-much-deadlier-30-than-20/index.html | N2 source re-read carried forward: [related-grip] The linked page describes which axle "saturates its friction circle first"; this layer carPos uses constant deceleration.
- CONFIRMED | (added) Still Doing Fifty Where You Stopped | git show 58f60be9ab:public/strata/why-stopping-distance-quadruples/index.html | N2 source re-read carried forward: [added-title-why-stopping-distance-quadruples] The omitted linked work title is exactly the h1 of the pinned target page. The source-record related entry describes the work without naming its title.
- CONFIRMED | (added) The Trip That Flips the Fear | git show 58f60be9ab:public/strata/the-trip-that-flips-the-fear/index.html | N2 source re-read carried forward: [added-title-the-trip-that-flips-the-fear] The omitted linked work title is exactly the h1 of the pinned target page. The source-record related entry describes the work without naming its title.
- CONFIRMED | (added) All-Wheel Go, Not All-Wheel Stop | git show 58f60be9ab:public/strata/does-awd-help-in-snow/index.html | N2 source re-read carried forward: [added-title-does-awd-help-in-snow] The omitted linked work title is exactly the h1 of the pinned target page. The source-record related entry describes the work without naming its title.
- CONFIRMED | (added) Push Wide, or Step Out | git show 58f60be9ab:public/strata/understeer-vs-oversteer/index.html | N2 source re-read carried forward: [added-title-understeer-vs-oversteer] The omitted linked work title is exactly the h1 of the pinned target page. The source-record related entry describes the work without naming its title.

## Findings

- [fixed] X1 (tefft-sample-552): changed the lead from 552 to the analysed sample of 422, with age and vehicle scope; shared dated correction with X15.
- [fixed] X2 (dft-retraction-year): changed the hint to the documented 2010 acknowledgment, with one shared dated correction for all chronology copies.
- [fixed] X3 (dft-retraction-year): replaced the invented 90% quotation with the source's 80% wording and corrected the event description and year; included both changes in the shared dated line.
- [fixed] X4 (dft-retraction-year): dated the reported acknowledgment to 17 September 2010 while retaining the minister attribution.
- [fixed] X5 (penning-quotation-truncated): restored the quotation's comma and omitted ending, with its own dated correction.
- [fixed] X6 (british-risk-as-rosen): attributed the 7%/31% pair to British OTS and police fatal file data and linked Richards Table 4.1; shared dated correction with X12, X14 and X21.
- [declined] X7 (reaction-detents-unsubstantiated), MINOR: tier C lists loose labels for illustrative model choices. The source does not measure these named states, but does not make the times impossible; no separate WRONG correction touches this hint.
- [declined] X8 (texting-reaction-unsubstantiated), MINOR: the source describes surprise incursion, not texting. Tier C requires listing the illustrative label; X9 was rejected, so the same-sentence exception does not apply.
- [declined] X10 (live-check-overclaim), MINOR: the wet handler leaves the transcript stale. The triage explicitly classifies every-number checking overclaims as MINOR and requires listing this heading at tier C.
- [declined] X11 (live-check-overclaim), MINOR: wet/reset leave previous values in the transcript. The triage requires listing the checking-completeness overclaim at tier C; no handler change was made.
- [fixed] X12 (british-risk-as-rosen): replaced the false two-anchor German fit with the published equation, in the page, model comments, README and both verifier copies.
- [declined] X13 (curve-difference-causes-overstated), MINOR: Richards offers possible contributors, not a measured decomposition. Tier C requires listing this separate sentence, which is not part of the corrected German-anchor attribution.
- [fixed] X14 (british-risk-as-rosen): revised the scope note and README to identify each model's actual provenance.
- [fixed] X15 (tefft-sample-552): replaced the footer and README count and preserved the analysed age and vehicle scope; shared X1's dated correction.
- [fixed] X16 (aaa-report-link-obsolete), MINOR: changed AAA 2018/02 to the working 2026/02 report URL in the footer and README. The same-sentence exception applies with X15; no separate page correction line.
- [declined] X17 (live-check-overclaim), MINOR: retained the dek/meta checking sentence under the triage's tier C instruction, with the stale transcript and five-anchor audit limitations recorded.
- [fixed] X18 (dft-retraction-year): replaced the false chronology in JSON-LD and removed formal-withdrawal wording from the markdown dek and meta description.
- [dated] X19 (jsonld-modified-date-stale): set JSON-LD dateModified to 2026-10-14 for this revision. No Updated line under the explicit user exception; the five Corrected lines date the changes.
- [fixed] X20 (fatality-risk-without-collision): made zero residual produce exactly zero collision fatality risk across the street outputs, annotations and calculation; corrected the on-page self-check and offline assertion, and added served-script regression checks with a positive-impact control. Added a dated correction.
- [fixed] X21 (british-risk-as-rosen): the shared German model now generates the equation (2) values and ratio in all dependent outputs; the verifier checks the actual table cells.
- [fixed] X22 (dft-retraction-year): corrected the canvas literal and its verifier assertion to the 2010 acknowledgment; updated the README copy.