Ibn workin' on the railroad

Between Mecca and Medina. When you want something done cost effectively, you rely on motivation the old fashioned way; 

The Spanish-led consortium that in September 2011 won the €6.7-billion contract to build a high-speed rail link between Medina and Mecca has spent the last year studying satellite photographs in a bid to deal with the biggest challenge it faces: preventing Saudi Arabia’s ever-shifting sands from swallowing its track.

....The Saudis have said they will not pay overrun costs, which means that unless the Spanish consortium wants to lose money on the project, it must find a way to prevent sand from damaging the track and equipment.

Then there are a few other issues;

...the biggest challenge to getting the trains running on time will come from the estimated 60 million passengers per year who will make the 450-kilometer journey between Mecca and Jeddah as they undertake the two Islamic pilgrimages, Hajj and Umrah. “We’re talking about a train leaving every 10 minutes with men and women separated, many of whom will not speak English or Arabic; Muslims from all over the world, some of them poor, who perhaps are abroad for the first time, and will be carrying huge amounts of luggage and won’t want to be separated from what is perhaps all they own in the world, which they may need to sell to make what will probably be the only journey in their lives: to Mecca,” says a source at the consortium. “And on the way back, they will want to bring huge water containers to share out in their village.” He points out that trains will run 23 hours a day, with just one hour for maintenance.

The consortium is also required to provide a train for the exclusive use of the Saudi royal family. 

Not to mention;

Having to work within the confines of Saudi Arabia’s strict interpretation of Islam has also proved a challenge, says the consortium: “Women are not allowed out in public unless accompanied by a male guardian, so it has been very difficult getting visas for our female staff.” Non-Muslims are not allowed into the holy sites of Mecca and Medina, so the consortium has had to teach Muslims to drive the trains. At the same time, it has also had to build makeshift mosques at its construction sites for a workforce that prays five times a day. 

It is written, in the contract.