These are truly exciting times to be in transportation research. Cities around the globe are reviving their public transit systems to enhance the reach, connectivity, and travel market share of buses and trains. A variety of shared mobility modes have emerged and been on the rise, thanks to smart phones and sharing economy. Various combinations of technology and policy solutions are being experimented to address traffic congestion and other externalities of transportation. And not the least, large data streams are becoming available for use in transport planning and operations. Yet, traffic congestion, traffic related pollution and other public health problems attributable to transportation continue to be on the rise in most cities of the world.

Keeping the above trends in view, this special issue on Transportation Research features a set of six invited papers by leading researchers on the following topics: public transit systems and car ownership in emerging economies, bicycle sharing systems, connected and automated vehicles, and use of emerging data sources for transport planning. The papers not only discuss the topics in detail, but also review the mathematical modelling methods used and outline an agenda for future research in these topics. In addition, a discussion paper provides a reader-friendly overview of the network science aspects associated with the traffic congestion problem, why seemingly common-sense approaches to reduce congestion do not often work, and ways to decongest cities.

Elephant and six blind men is analogy for the confusion scientist had in understanding hydrogen bonding. The idea was to use the elephant as an illustration of hydrogen bonding, which has confused most of the Scientists over a century leading to different views.

In general, the bigger molecules have higher boiling point as you can see from hydrocarbons. Smaller ones like methane and ethane are gases, slightly larger ones as butane, pentane and hexane are liquids and even bigger ones such as paraffins are solids. Chemists realized that water has bydrogen bonding which makes it a liquid at room temperature, which has helped life evolve on the planet. Moreover, our DNA double helix is held together by the hydrogen bonds helping in safe and accurate transfer of the genetic code. It was assumed that hydrogen sulphide and hydrocarbons do not form hydrogen bonds and our lab and many others have shown that they can also form hydrogen bonds.