The research, published in Frontiers in Future Transportation, was conducted by a team spanning the University of Palermo, Monash University Accident Research Centre in Australia, and Shenzhen University in China. Led by Muhammad Yasir of the University of Palermo, the study examined 141 pedestrian crashes recorded by the Palermo Municipal Police between 2015 and 2022, comprising 54 fatal crashes and 87 serious injury crashes. Rather than relying on posted speed limits or average travel speeds alone, the team used percentile travel speeds — the 15th, 50th, and 85th percentiles — drawn from TomTom Move, a traffic analytics platform built on anonymized GPS data from vehicles across the road network.

The choice of percentile speeds is technically significant. Impact speed, the velocity at which a vehicle actually strikes a pedestrian, is the most direct determinant of injury severity, but real-world crash data rarely capture it accurately. Police reports tend to be biased toward severe outcomes, and individual crash-involved vehicles may have been traveling far above or below the prevailing traffic speed. Percentile speeds offer a workaround: they characterize the full distribution of driver behavior at a crash location, capturing the slower, typical, and faster ranges of the speed environment. Prior research has shown that mean speed alone is a poor predictor of traffic injuries and that crash severity varies significantly with the speed distribution.

To make the speed data meaningful, the researchers extracted only the one-hour interval corresponding to each recorded crash time from a month of TomTom observations covering all hours and days of the week. If a crash occurred at 12:45 pm, only the 12:00 to 1:00 pm speed data was used. For the 54 fatal crash locations, estimates were derived from 29,208 route observations; for the 87 serious injury locations, from 41,938 observations. The team then applied established ordered logit risk functions, using the parameter estimates for the 15-to-59 age group as a broad reference category, to estimate the probability of fatal and serious injury (FSI) at each percentile speed.

The results reveal a steep, positive relationship between speed and pedestrian injury risk. At fatal crash locations, the estimated fatality risk was 0.7 percent at the 15th percentile speed (mean 20.1 km/h), 2.6 percent at the 50th percentile (mean 30.5 km/h), and 8.2 percent at the 85th percentile (mean 41.5 km/h). For serious injury crashes, the risks were far higher: 13.0 percent, 26.8 percent, and 43.6 percent at the 15th, 50th, and 85th percentile speeds respectively. Notably, the gap between the 50th and 85th percentiles was much larger than between the 15th and 50th, suggesting that the faster end of the driver speed distribution — where drivers may struggle to adjust to sudden changes in traffic conditions — drives a disproportionate share of severe pedestrian outcomes.

The counterfactual analysis is where the findings become actionable. The researchers mathematically reduced the entire percentile speed distribution at each crash location by 3 km/h and then by 5 km/h, and recalculated FSI risk. A 3 km/h reduction cut average fatality risk by 30.5 percent at the 15th percentile, 26.1 percent at the 50th, and 21.1 percent at the 85th. For serious injuries, the reductions were 23.0, 17.5, and 11.6 percent respectively. With a 5 km/h reduction, the benefits grew dramatically: fatality risk fell by 45.6 percent at the 15th percentile, 40.0 percent at the 50th, and 32.6 percent at the 85th, while serious injury risk dropped by 36.0, 28.1, and 19.4 percent.

These numbers carry particular weight in the Italian context. In 2024, Italy recorded 470 pedestrian fatalities, the second-highest in the European Union after Romania, and 72 percent of Italian pedestrian deaths involved cars as the main collision opponent — exceeding the EU average of 65 percent. According to the Italian National Institute of Statistics, pedestrians experience a fatality rate of 2.7 per 100 crashes, 4.4 times higher than car occupants. Palermo itself recorded 1,999 pedestrian crashes between 2015 and 2022, and its historic urban layout, dense pedestrian activity, and heavy reliance on private motorized travel — cars and motorcycles account for 69.2 percent of weekday trips — make it a textbook environment for vehicle-pedestrian conflict.

The study also documents the consequences of non-compliance. At one fatal crash site on Viale Ercole, where the posted limit is 50 km/h, TomTom data recorded 15th, 50th, and 85th percentile speeds of 52, 70, and 92 km/h during a one-month sample — evidence of frequent and substantial speed limit violations. The authors argue that intelligent enforcement tools such as speed cameras could help ensure compliance with reduced limits, and they point to the Movement and Place framework, which classifies streets by their mobility and social functions, as a way to justify lower limits in pedestrian-priority zones such as historic centers, school districts, and tourist areas. Palermo has already introduced limited traffic zones, pedestrian areas, and 30 km/h zones, and has pedestrianized more than 340,000 square meters of its historic center.

The findings align with a growing international evidence base. A Toronto study found that reducing speed limits from 40 to 30 km/h resulted in a 28 percent reduction in pedestrian motor vehicle collisions, while a Seattle case study showed that lowering limits by roughly 8 km/h led to a 17.2 percent decrease in crash severity and a 19.9 percent reduction in crash frequency. Traffic calming measures in Ghana, pedestrian hybrid beacons in the United States, and enhanced crosswalk lighting have all demonstrated complementary pathways to slower, safer streets. The Palermo study adds a crucial technical dimension: because it uses percentile speeds rather than single-dimensional measures, it captures the effect of speed variability across the distribution — showing that reductions applied across the entire speed environment, not just at the fastest end, yield meaningful safety gains.

The authors acknowledge limitations. Pedestrian ages were recorded only as a broad binary category, preventing age-specific risk estimation, and the injury risk model was not calibrated with Palermo or Italian crash data, so the estimated risks should be read as comparative estimates within the counterfactual framework rather than locally calibrated absolute probabilities. The TomTom speeds, derived from floating car data, were not independently validated against on-site radar measurements, though prior Italian research comparing commercial floating car data with fixed radar found reasonable estimates of urban travel speeds. Still, the core message is unambiguous: in dense historic cities where pedestrians and cars share constrained streets, shaving a few kilometers per hour off the entire traffic speed distribution could prevent a substantial share of the deadliest and most life-altering crashes. For urban planners and policymakers, the study suggests that the cheapest life-saving intervention may not be new infrastructure at all, but simply slowing down what already moves through the city.

Subject of Research: A study of vehicle-pedestrian crashes in Palermo, Italy, quantifies how percentile travel speeds affect pedestrian injury risk and shows that modest speed reductions of 3 to 5 km/h could meaningfully reduce fatal and serious pedestrian injuries.

Article Title: Evaluating the role of speed reduction on the severity of vehicle-pedestrian crashes: a case study in Palermo, Italy

Article References: Yasir, M., Logan, D., Migliore, M., D’Orso, G., Pervez, A., & Koppel, S. (2026). Evaluating the role of speed reduction on the severity of vehicle-pedestrian crashes: a case study in Palermo, Italy. Frontiers in Future Transportation, 7, Article 1805850. https://doi.org/10.3389/ffutr.2026.1805850

Image Credits: AI Generated

DOI: 10.3389/ffutr.2026.1805850

Keywords: pedestrian safety, vehicle speed, speed reduction, traffic crashes, Palermo, Italy, injury severity, road safety, percentile speeds, traffic calming, urban mobility, counterfactual analysis

The study, published in Archaeological and Anthropological Sciences by Viva Sacco, Patrick Sean Quinn, and Corisande Fenwick of University College London’s Institute of Archaeology, analysed 188 ceramic samples from five Sicilian sites: Palermo, Castello della Pietra, Piazza Armerina, Agrigento, and Syracuse. By combining three complementary techniques, macroscopic fabric analysis, thin-section petrography, and instrumental neutron activation analysis, the team tested and refined earlier classifications that had relied largely on visual inspection. The result is the most detailed compositional fingerprint yet of Sicily’s glazed ceramic industry between the late ninth and twelfth centuries.

Glaze technology arrived in Palermo in the late ninth century, almost certainly carried by mobile artisans or through technology transfer from nearby Ifriqiya, the region of modern Tunisia and eastern Algeria that had recently conquered the island. For nearly a hundred years, Palermo remained Sicily’s sole centre of glazed ware production, supplying a modest local market that only began to expand in the mid-tenth century. Then, by the late tenth century, new workshops emerged across the island, breaking Palermo’s monopoly and shifting the industry from a single-centre model to a polycentric one. This Sicilian trajectory contrasts sharply with Ifriqiya, where multiple production centres, led by Kairouan, operated from an early stage and glazed tableware was already widely distributed by the late ninth century.

The analytical challenge facing the researchers was considerable. Sicilian and Ifriqiyan glazed wares share such strong similarities in vessel forms and decoration that scholars have long lumped them together under the vague label ‘Siculo-Maghrebin’, obscuring internal developments and regional specificities. Compounding the problem, no kilns dating from the late ninth to the eleventh centuries have ever been excavated in Sicily. Production centres have instead been identified through scattered finds of wasters, kiln rods, and recurring petrographic groups, at Palermo, Mazara del Vallo, Agrigento, Syracuse, Paternò, and the rural settlement of Piazza Armerina.

The clearest and most coherent group identified in the new study corresponds to wares produced in Palermo. Petrographic Fabric 1, the so-called Ficarazzi fabric, accounts for 114 of the analysed samples and is defined by a non-calcareous matrix dominated by monocrystalline quartz and frequent micritic limestone. This fabric matches the famous ‘Ficarazzi clay’, a grey-blue alluvial deposit of Lower Pleistocene age located roughly one kilometre east of the medieval city, near the mouth of the Eleuterio River. Remarkably, this clay source had been exploited since at least the Punic period and remained in use into the early twentieth century. Geochemical analysis confirmed the picture: a compact compositional cluster of 89 samples, characterised by elevated concentrations of cobalt, caesium, manganese, and rubidium, corresponds tightly to the Palermitan material, demonstrating a highly consistent paste recipe and the exploitation of a restricted range of raw materials.

Beyond Palermo, the study characterised the products of several other workshops that began operating from the late tenth century. At Syracuse, Petrographic Fabric 2 contains abundant carbonate inclusions and volcanic rock fragments, features consistent with the volcanic geology of eastern Sicily, and was tempered with limestone and weathered mafic material. At Piazza Armerina, Fabric 4 is a biotite-rich calcareous sandy quartz fabric whose mineralogical variability matches the complex local sedimentary formations around the Villa del Casale, where kiln bars have been discovered. At Agrigento, Fabric 6, sampled from sherds recovered near the kilns and production waste of the Fornaci S. Lucia artisanal district, corresponds well with the local geology of calcareous tuffs, fossiliferous marine clays, and shell breccias.

Not every attribution proved straightforward. The fabrics tentatively assigned to Mazara del Vallo, represented by samples from the rural hilltop site of Castello della Pietra, displayed a bimodal quartz distribution and calcareous matrices that overlapped chemically and petrographically with North African products. These samples scattered across multiple geochemical clusters, underscoring the genuine difficulty of distinguishing some Sicilian and Ifriqiyan calcareous fabrics. The researchers suggest this may reflect technological convergence, shared production traditions, or the exploitation of geologically comparable clay sources on both sides of the Strait of Sicily, though the smaller sample sizes for these groups also limit the statistical robustness of the groupings.

The geochemical work itself demanded unusual care. Because the entire assemblage consisted of glazed ceramics, the team had to assess whether lead-rich glazes, containing 40 to 65 weight percent lead oxide, had contaminated the bulk compositions of the ceramic bodies. Scanning electron microscopy with energy-dispersive spectroscopy of 120 samples revealed that most specimens showed either no glaze-body interaction layer or only a very thin one. The ceramics had also undergone a double-firing process, in which the body was bisque-fired before glazing, fixing the body’s composition before the glaze was applied. Statistical tests showed that elements associated with glaze colourants, such as manganese and iron, did not influence the multivariate structure of the dataset, confirming that the compositional groups reflect the ceramic fabrics themselves rather than glaze contamination.

Perhaps the most evocative technological finding concerns a shared craft practice. Nearly all the Sicilian and North African samples displayed a light-coloured vitrified layer beneath the glaze, between 0.25 and 1.5 millimetres thick, formed when salt deliberately mixed into the clay migrated to the surface during drying and locally fluxed the clay minerals, producing a ‘salt-white’ surface treatment. This technique, employed by Sicilian and North African artisans since at least the Punic period and still used by potters in Tunisia today, along with the consistently high firing temperatures evident from the low optical activity of the clay matrices, points to a body of common technical knowledge circulating between production centres in Sicily and Ifriqiya, likely transmitted through the mobility of artisans and specialised networks of technological exchange.

The study also yielded a surprise: a single sample from Palermo, classified as Fabric 12, proved to be a clear outlier whose petrographic characteristics and splashed-ware typology point to an Egyptian origin, hinting at trade connections extending beyond the immediate Sicily-Ifriqiya axis. By establishing preliminary petrographic and geochemical reference groups for Sicilian glazed wares, the research provides a framework for future provenance studies and for identifying Sicilian exports at consumption sites across the medieval Mediterranean. The authors emphasise that expanding the comparative dataset, particularly for North African products and underrepresented Sicilian workshops such as Paternò, will be essential for refining these groups and reconstructing the full pattern of production, exchange, and technological interaction that accompanied Islamisation in the central Mediterranean.

Subject of Research: Archaeometric characterisation of Islamic-period glazed ware production centres in Sicily

Article Title: Tracing glazed ware production in Islamic Sicily: macroscopic, petrographic, and geochemical evidence

Article References: Sacco, V., Quinn, P. S., & Fenwick, C. (2026). Tracing glazed ware production in Islamic Sicily: macroscopic, petrographic, and geochemical evidence. Archaeological and Anthropological Sciences, 18(9), Article 195. https://doi.org/10.1007/s12520-026-02550-1

Image Credits: AI Generated

DOI: 10.1007/s12520-026-02550-1

Keywords: Islamic Sicily, glazed pottery, ceramic petrography, geochemistry, Palermo, Ifriqiya, medieval ceramics, archaeometry, Ficarazzi clay, thin-section petrography, INAA, cultural heritage