An informal survey of some big engineering companies reveals that a down economy and security concerns are keeping more engineers tied to their desks these days. Many firms say they have restrictions in place, allowing travel only when it involves meeting with customers or other essential can't-be-done-over-the-web-or-phone activities. Texas Instruments, for example, clamped down on nonessential travel two years ago as a cost-savings measure. Recently, it has started to further restrict travel based on security issues and foreign travel advisories. But once the economy perks up, don't reach for your carry-on bag. E-learning, video conferences, and collaborative tools are gaining traction as effective alternatives to travel.