The decision for or against a river crossing depends on a number of questions regarding both costs and engineering challenges.

The construction of the bridge's structure presented major engineering challenges.

The human exploration of Mars presents a massive engineering challenge.

Despite the simplicity of the materials, there were some engineering challenges.

The real engineering challenge is getting that cost down to where it's a mass-market product.

In addition to the engineering challenges, pioneers face uncertainty about their legal rights.

It's a seemingly simple idea that has proved to be an extraordinary engineering challenge.

Running of the first metro car on the line by 1984 was considered a great engineering challenge.

From the beginning, the Citigroup Center was an engineering challenge.

Do they really believe that a new spacecraft will come without an engineering challenge or a human toll?