Comparative assessment of black carbon levels in public transit systems across three cities
Bibliographic record
Abstract
This research investigates users’ exposure to black carbon (BC) in subways, buses, and BRTs. The study was conducted in Mexico City and Puebla (Mexico) and Montreal (Canada) to identify city-specific variations across modes and factors associated with levels of BC. Over 1500 min were collected, and regression model analyses were used to identify the impacts of mode and other factors. Among all measured transit modes, subway systems exhibited the highest BC concentrations (median: 10.83 μ g / m 3 ; MAD: ±6.97 μ g / m 3 ). In contrast, BRT systems showed the lowest exposure levels (3.7228 ± 2.27 μ g / m 3 ), with buses demonstrating comparable concentrations (4.00 ± 2.22 μ g / m 3 ). Notably, high concentrations in subways are primarily observed in segments where the subway operates in underground tunnels. Both surface transit modes measured slightly above ambient outdoor levels (2.82 ±1.66 μ g / m 3 ), suggesting minimal additional exposure during above-ground commute. • 42% of the observations in Montreal values above the accepted limit of 3.5 μ g m − 3 . • In Mexico, 60% of observations in BRTs and 84% in subways surpass the threshold. • In Puebla, 78% of BRT’s observations and 59% of buses surpass the 3.5 μ g m − 3 limit. • Excessive BC levels in subway trains are linked with tunnels along the route. • Engine technology plays a fundamental role in buses and BRTs.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".