SITs are, by definition, alone. But ‘alone’, is not an emotion. It merely means “no one is nearby.”  ‘While ‘loneliness’ is the mind’s self-perceived emotional state of feeling unattached or unwanted.             

Generally, I prize being alone; prizing it’s solitude, freedom & privacy, yet I am quite capable of engaging
with others.

I can be alone ‘in-my-thoughts’ while wandering in an Asian crowd of thousands OR actively engaged with fellow travelers cooking dinner in my hostel’s kitchen. 

I am a contented introvert or extrovert when it pleases me.  

I relish my thoughts as I stroll down a small village path trying to be attuned to every little thing I see & hear:   a Myanmar bush covered with butterflies, two Normandy ladies working in their garden waving back, or luscious luncheon aroma & haunting music wafting out of a Syracuse, Sicily’s back street home.

I am an anonymous human speck in the flow of humanity’s traffic.

      Anecdote: traveling alone -- GREAT IRONY: At 28, having won a free TV Dating Game ttrip to Italy, I extended trip to other countries, but after a couple of weeks, I realized I was 'lonely'; my experience too shallow without someone to share it with...

      Then, at 46, an ex-girlfriend & I planned a camping road trip to Vancouver, BC's "1986 World Exposition", but, alas, she stood-me-up at the last moment. Let down, I indignantly vowed to go alone in spite of my feared 'loneliness.'      I visited the Exposition, several national parks, historical sites & realized how fascinating were the thoughts in my own brain AND how exhilarating a 'solo' experience.  I've mainly traveled alone since then.

OTOH, my gregarious friend Lauren invariably meets another woman traveler and they travel together then and sometimes on future trips.

        Tour Bus & Cruise tourists rely on the security & comfort of that their modest sized tour group or town-sized cruise crowd, finding privacy when needed in their sleeping room.