Examining exposure of motorcycles at signalized intersections

Crash statistics in Singapore from 2001 to 2005 have shown that motorcycles are involved in about 54% of intersection crashes. The overall involvement of motorcycles in crashes as the not-at-fault party is about 43% but at intersections, the corresponding percentage is increased to 57%. Quasi-induced exposure estimates show that the motorcycle exposure rate at signalized intersections is 41.7% even though motorcycles account for only 19% of the vehicle population. This study seeks to examine in greater details, the problem of motorcycle exposure at signalized intersections. In particular, the exposure arising from potential crashes with red light running vehicles from the conflicting stream at four signalized intersections is investigated. The results show that motorcycles are more exposed because they tend to accumulate near the stop-line during the red phase to facilitate an earlier discharge during the initial period of the green which is the more vulnerable period. At sites where there are more weaving opportunities because the lanes are wider or where there are exclusive right-turn lanes, the accumulation is higher and hence an increased exposure is observed. The analysis also shows that the presence of heavy vehicles tends to decrease motorcycle exposure as their weaving opportunities become restricted as well as there is a greater reluctance for them to weave past or queue alongside the heavy vehicles and their effects intensify for narrower lane width

Investigation of soil property changes and olive tree stress as caused by excessive sewage-sludge application

This study was undertaken to assess the impact of a single excessive sludge application (300 Mg ha-1) on the soil surface of an olive orchard several years after the event. Selected soil properties were compared in two soil profiles, one in the sludge-amended field and another in an adjacent unamended field of naturally growing trees. Leaf analysis included macronutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg)], trace elements [copper (Cu), zinc (Zn), manganese (Mn), iron (Fe), nickel (Ni), boron (B)], and isotopic composition (δ 15N and δ 13C). Soil pH and other chemical properties were increased in the surface soil and the root zone of the sludge-treated profile in comparison to those of the untreated control. The multifold increase of Bray P and nitrates indicated a serious risk for dissolved phosphates in runoff and nitrate contamination of groundwater. Trace-element content also increased, but not greater than the critical soil concentration. Olive trees responded to excessive sludge application by increased N uptake as evidenced by increased leaf N content and elevated 15N signal. The increased leaf δ 13C signal of the leaves further indicated tree stress in the sludge-amended field during the summer growing season in comparison to the naturally growing control trees. Isotopic composition, leaf nutrient, and trace element concentration did not reveal the causes of leaf tip burning in half of the trees of the sludge-amended field. Copyright © Taylor & Francis Group, LLC