Hewlett-Packard Co. agreed to buy the automotive design-tool business of Siemens Automotive, a unit of Germany's Siemens, for an undisclosed amount. The tools are used to design, calibrate and test the electronic controls used in automobile engines and transmissions. The companies said Palo Alto-based Hewlett-Packard will take over the business in phases over the next 18 months. HP said the purchase will give it immediate links to automotive original equipment manufacturers and electronic suppliers. Hewlett-Packard said it will push for the industry to adopt the Siemens technology as a standard when designing controls for powertrains. Companies then can focus on powertrains instead of worrying about the tools it takes to design them, said John Weidert, general manager of HP's integrated systems division. Hewlett-Packard shares rose $2.50 to close at $59 on the NYSE.